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University  of  California, 


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ELECTRIC  POWER  TRANSMISSION  PLANTS 


USE  OF  ELECTRICITY  IN  MINING  OPERATIONS. 


By  THOMAS  HAIGHT  LEGGETT, 

Bodie,  Mono  County,  California. 


[Written  for  the  Twelfth  Report  of  the  State  Mineralogist,  1894.] 


(uhivbrsitt] 


sac;ramento: 

STATE    OFFICE,      :       I       :       A.    J.    JOHNSTON,    SUPT.    STATE    PRINTING. 

1894. 


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ELECTRIC  POWER  TRANSMISSION  PLANTS  AND  THE  USE 
OF  ELECTRICITY  IN  MINING  OPERATIONS. 

By  Thomas  Haight  Leggett,  of  Bodie,  Mono  County,  California. 


Some  one  has  aptly  spoken  of  California  as  the  Switzerland  of 
America.  Certainly  the  rugged  scenery  of  its  snow-capped  Sierra,  and 
its  numerous  lakes  and  mountain  streams,  justify,  in  part,  the  simile. 
In  Switzerland  they  have  been  quick  to  realize  the  advantages  to  be 
derived  from  the  utilization  of  their  water  powers  for  the  generation  of 
electric  power,  and  its  transmission  to  distant  points;  here,  in  California, 
we  are  but  beginning  to  grasp  the  situation. 

In  electricity  the  miner  has  undoubtedly  gained  a  most  efficient  and 
valuable  ally.  Through  its  aid  the  latent  power  of  the  many  streams 
now  running  idly  down  the  mountain  slopes  can  be  made  available,  and 
brought  across  long  stretches  of  country  by  means  of  a  simple  line  of 
wire,  to  operate  the  machinery  of  mine  and  mill. 

In  sections  where  no  water  powers  are  available,  and  fuel  is  scarce 
and  dear,  electricity  may  be  generated  at  the  center  of  fuel  supply,  and 
the  power  transmitted  from  this  central  station  to  operate  a  number  of 
mills  and  hoisting  works  in  the  distant  mining  camp.  One  of  the  great 
advantages  of  electric  power  is  its  adaptability  to  ready  subdivision 
into  small  units  without  material  loss  of  power,  by  reason  of  the  high 
efficiency  now  developed  by  the  best  types  of  dynamos.  Hence,  separate 
motors  may  be  used  in  the  mill  for  running  crushers,  stamps,  concen- 
trators, pans,  etc.,  or  in  the  mine  for  hoisting-engines,  pumps,  and  air 
compressors,  effecting  a  very  appreciable  saving  when  any  of  these 
machines  are  idle.  To  accomplish  this  requires  the  use  of  the  direct 
current,  but  this  can  be  readily  obtained  from  the  alternating  where 
such  is  used  for  the  transmission,  by  employing  rotary  transformers,  or 
"  motor  generators, '^  of  high  efficiency. 

In  a  letter  to  the  writer,  accompanying  photographs  illustrating  the 
Telluride,  Colo.,  transmission  plant,  hereinafter  described,  Mr.  Chas.  F. 
Scott  gives  the  following  excellent  resume  of  the  present  status  of  elec- 
tricity in  the  field  of  mining: 

"In  the  introduction  of  electrical  apparatus  to  the  operations  of  the 
mining  industries  of  the  West,  the  field  of  electrical  power  transmission 
is  extending  upon  lines  which  have  already  been  well  established  in 
other  industries.  The  electric  motor  is  becoming  an  important  factor  in 
almost  every  industry  in  which  power  is  utilized.  One  of  the  most  nota- 
ble instances  is  in  electric  traction.  The  electric  street  railway  motor 
has  not  only  almost  entirely  replaced  animal  power,  but  it  has  wonder- 
fully increased  the  speed,  comfort,  and  economy  of  street  railway  opera- 
tion, and  has  also  extended  it  to  distances  and  classes  of  service  which 
were  previously  impracticable.  The  early  railway  motor  had  many 
and  peculiar  difficulties  to  overcome,  but  the  problems  incident  to  it 
have  been  rapidly  surmounted. 

''  Results  similar  to  those  which  have  been  attained  in  street  railway 
working  are  to  be  anticipated  in  the  application  of  the  electric  motor 


to  the  mining  industry.  Not  only  will  the  work  which  is  now  performed 
be  done  in  many  cases  with  increased  ease  and  economy,  but  the  intro- 
duction of  the  motor  will  lead  to  new  methods  of  operation.  Mining 
possesses  many  difficult  and  peculiar,  requirements  for  the  application 
of  power.  The  motor,  on  the  other  hand,  possesses  characteristics  which 
render  it  capable  of  being  adapted  to  a  very  great  variety  of  conditions. 

''The  work  which  has  already  been  accomplished  in  the  new  plants 
which  have  been  installed,  promises  much  for  the  future.  The  firsu 
work  has  been  under  difficulties  which  are  incident  to  every  new  under- 
taking. The  principal  difficulties  which  have  manifested  themselves 
are,  however,  not  fundamental  ones;  they  are  principally  due  to 
mechanical  difficulties  which  are  more  or  less  readily  recognized,  and 
usually  indicate  a  ready  method  of  solution.  A  second  trouble,  which 
has  promised  at  times  to  be  very  serious,  is  the  effects  resulting  from 
the  atmospheric  conditions  in  the  mining  country.  Lightning  in  many 
places  has  been  extremely  severe,  and  methods  of  protection  were 
required  which  were  impossible  to  devise  before  the  conditions  had  been 
learned  from  experience.  The  necessity  for  protection  has  been  fol- 
lowed by  the  means  of  protection,  and  electrical  installations  need  no 
longer  be  in  peril  from  lightning,  if  properly  protected. 

"  The  experience  and  progress  which  have  come  from  other  applications 
of  electricity  can  be  taken  advantage  of  in  application  to  mining  work. 
The  constant  improvements  and  advances  which  are  being  made  in  the 
manufacture  of  electrical  apparatus  make  it  possible  to  secure  at  the 
present  time  apparatus  which  is  better  adapted  for  its  work  than  could 
have  been  secured  a  few  years  ago. 

"  There  is  often  an  apprehension,  on  the  part  of  those  who  are  not 
familiar  with  electrical  apparatus,  that  it  is  a  fundamental  failure  if  it 
does  not  at  once  begin  and  continue  in  satisfactory  operation.  Those, 
however,  who  are  acquainted  with  electrical  machinery,  and  who  under- 
stand the  nature  of  the  difficulties  which  develop,  may  readily  see  that 
the  fundamental  elements  in  electrical  power  transmission  and  distri- 
bution are  not  involved  in  these  difficulties,  but  that  they  arise  from 
incidental  features  which  can  be  readily  corrected.  The  work  which  has 
already  been  accomplished  shows  the  possibilities  which  are  open  in  the 
field  of  electrical  mining,  and  promises  much  for  the  future." 

The  transmission  of  100  horse-power  a  distance  of  109  miles,  from 
Frankfort  to  Lauffen,  Germany,  in  1891,  showed  conclusively  that  from 
an  engineering  standpoint,  at  least,  the  transmission  of  power  over  long 
distances  by  electricity  was  perfectly  practicable;  though  in  this  par- 
ticular instance  it  was  not  a  commercial  success,  nor  was  it  intended  to 
be,  since  the  power  was  used  for  exhibition  purposes  only.  Since  then, 
however,  plants  have  been  installed  both  in  Europe  and  in  the  United 
States,  and  are  to-day  successfully  transmitting  electricity  for  lighting 
and  power  purposes  over  distances  ranging  from  1  to  30  miles. 

It  will  be  proper  to  outline  here  the  various  methods  of  transmitting 
power  over  long  distances  by  electricity,  but  for  full  information  on  this 
subject  recourse  must  be  had  to  the  technical  writers  in  the  electrical 
journals  and  society  transactions.* 

*See  W.  F.  C.  Hasson's  paper  on  "Electric  Transmission  of  Power  Long  Distances," 
Transactions  of  the  Technical  Society  of  the  Pacific  Coast,  Vol.  X,  No.  4;  "Long  Dis- 
tance Transmission  for  Lighting  and  Power,"  by  Chas.  F.  Scott,  E.E.,  Vol.  IX  of  Trans- 
actions of  American  Institute  of  Electrical  Engineers;  also  pamphlet  on  Long  Distance 
Transmission  by  L.  B.  Stillwell,  E.E.,  issued  by  Westinghouse  Electrical  and  Manufact- 
uring Co.,  Pittsburg,  Pa. 


Power  may  be  transmitted  by  means  of  electricity  by—  '   '^  1 

1st.  The  direct  or  continuous  current. 

^ (a) Single    phase,    2-wire  synchronous^^*>^ 
system. 

Either  synchro- 
(6) Two-phase,  4- wire 

system. 
( c )  Polyphase  system ; 
usually  3-phase 
with  3  wires. 


2d.  The  alternating  current  --< 


nous  or  inde- 
pendent speeds 
^  of  generator 
and  motor,  as 
desired. 


The  direct  or  continuous  current  has  the  advantage  that  the  motors 
are  self-starting,  and  at  practically  full  torque,  or  turning  effect.  The 
motor  speed  is  quite  independent  of  that  of  the  generator,  though  this  is 
not  necessarily  an  advantage,  inasmuch  as,  in  synchronous  systems,  the 
governing  of  the  generator  speed  regulates  that  of  the  motor  as  well, 
and  therefore  attention  to  the  speed  of  but  one  machine  is  all  that  is 
required. 

Direct-current  dynamos  labor  under  the  disadvantage  of  working 
under  comparatively  low  potentials,  since  they  require  a  commutator 
to  change  the  alternating  current  they  generate  into  a  continuous  one, 
i.  e.,  a  current  flowing  constantly  in  one  direction;  and  thus  far  it  has 
been  found  impracticable  to  insulate  this  commutator  for  very  high 
tensions.  While  it  is  asserted  that*  "direct-current  machines  of  5,000 
volts  are  in  regular  and  successful  use  for  arc-lighting,"  it  must  be  borne 
in  mind  that  the  requirements  for  furnishing  light  a  limited  number  of 
hours  each  day  are  very  different  from  the  demands  made  upon  electrical 
machines  by  a  stamp  mill  or  hoisting  works,  which  require  unintermit- 
tent  operation,  oftentimes  including  Sundays. 

Hence,  such  a  high-potential,  direct-current  machine,  if  in  good  run- 
ning order  to-day,  would  hardly  be  serviceable  for  long-distance  trans- 
mission, and  indeed  the  staunchest  advocates  of  the  direct  current  in 
this  country  have  never  installed  such  a  machine  for  this  purpose. 

On  the  contrary,  in  several  cases  where  electrical  companies  known 
to  favor  the  direct-current  system  have  had  contracts  for  the  installa- 
tion of  long-distance  transmission  plants,  they  have  not  attempted 
such,  but  have  instead  used  an  alternating-current  system  in  every 
case  where  the  distance  exceeded  three  miles. 

It  is  safe,  therefore,  to  conclude  that  until  these  difficulties  of  com- 
mutator insulation  are  overcome,!  this  distance  is  the  practical  limit 
for  direct-current  transmission,  unless  a  series  arrangement  of  gener- 
ators and  motors  be  resorted  to. 

A  low  potential  necessarily  limits  the  distance  of  transmission,  since 
the  size  of  wire  is  directly  proportional  to  the  number  of  amperes  of 
current  to  be  carried;  and  since  amperes  times  volts  equals  watts,  of 
which  746  are  equivalent  to  1  horse-power,  it  follows  that  to  transmit 

*  The  "  Electric  Transmission  of  Power,"  Engineering  Magazine,  June,  1894,  p.  393. 

+  Mr.  E.  H.  Booth,  in  an  article  entitled  "Electricity  as  applied  to  Mining  Operations," 
published  in  "Industry"  for  June,  1892,  says:  "It  is,  however,  a  matter  of  difficulty  to 
make  commutators  for  potentials  over  2,000  volts  for  direct-current  generators,  on 
account  of  the  ^^reat  number  of  segments  required,  and  the  difficulty  of  their  proper 
insulation.  While  this  voltage  will  be  efficient  and  economical,  both  as  regards  cost  of 
installation  and  of  operation  in  many  cases,  conditions  will  also  be  met  with  requiring 
much  higher  voltages,  which  are  at  present  commercially  practicable  only  through  the 
use  of  alternating  currents." 


—    6    — 

100  horse-power,  or  74,600  watts,  a  given  distance  at  a  pressure  of  500 
volts  (the  ordinary  voltage  of  a  direct-current  dynamo),  would  require 
a  current  of  149.2  amperes,  or  a  wire  six  times  as  large  (sectional  area 
six  times  as  great)  as  that  needed  to  deliver  the  same  amount  of  power 
over  the  same  distance  at  an  electrical  tension  of  3,000  volts  (25 
amperes  X  3,000  volts  =  75,000  watts  =  100  horse-power). 

The  series  arrangement  of  generators  and  motors  alluded  to  has  been 
introduced  abroad,  notably  in  Switzerland,  and  brought  there  to  a  higher 
state  of  perfection  than  in  this  country.  This  application  of  the  direct 
current  for  long-distance  transmission  requires  a  number  of  generators 
and  an  equal  number  of  motors,  making  a  complicated  apparatus  of 
excessive  first  cost,  especially  so  since  extra  dynamos  and  motors  must 
be  provided;  otherwise  an  accident  to  one  machine  disables  the  entire 
plant. 

At  Genoa,  Italy,  there  is  such  a  transmission  at  present  in  operation. 
The  power  transmitted  is  300  horse-power  over  a  distance  of  1 8  miles. 
At  the  power  stations,  of  which  there  are  three,  one  below  the  other, 
there  are  four  groups  of  dynamos,  each  group  of  two  dynamos  being 
driven  by  turbines  (Piccard  system)  of  140  horse-power,  working  under 
heads  varying  from  225  to  495  meters. 

These  dynamos  are  connected  in  series,  one  group  being  held  in  reserve 
in  case  of  accident  to  any  of  the  others,  and  produce  each  a  current  of 
47  amperes  at  1,000  volts  electrical  tension,  the  resulting  E.  M.  F.  some- 
times reaching  6,000  volts  during  the  hours  of  maximum  load.  The 
motors  are  also  connected  in  series,  no  one  machine,  it  will  be  noted, 
carrying  a  potential  exceeding  1,000  volts  at  any  time.  The  power  is 
utilized  in  operating  a  factory  at  the  terminus  of  the  line. 

The  lack  of  flexibility  of  the  system  and  its  inadaptability  to  a  wide 
and  varied  range  of  work  have  often  been  spoken  of  by  technical  writers, 
and  these  disadvantages  have  prevented  its  successful  competition  with 
alternating-current  systems  for  transmission — such  as  that  from  Niagara 
Falls  to  Buffalo,  where  the  power  is  to  be  utilized  for  a  great  variety  of 
work. 

It  has  been  cited  as  an  advantage  of  the  direct-current  system  that  it 
is  not  liable  to  trouble  from  the  static  capacity  and  self-induction  of  the 
line  occurring  with  the  alternating-current.  Self-induction  will  reduce 
the  potential  at  the  motor  end  of  .the  line,  while  static  capacity  will  act 
in  the  opposite  direction  and  increase  the  E.  M.  F.,  thus  tending  to  coun- 
teract the  effect  of  self-induction. 

The  discussion  of  these  technicalities  can  safely  be  left  to  the  elec- 
tricians, but  the  writer  can  state  from  experience  with  a  transmission 
by  the  alternating-current  synchronous  system  of  120  horse-power  ove^ 
a  distance  of  12^  miles  that  no  trouble  whatever  has  arisen  from  these 
causes.  (See  table  showing  the  line-loss  and  the  efficiency  of  this  trans- 
mission.) 

The  three  types  of  alternating-current  machines,  viz.,  the  single-phase 
synchronous,  the  double-phase,  and  the  three-phase  generators,  may,  for 
purposes  of  comparison,  be  likened,  respectively,  to  the  single-cylinder 
steam  engine,  the  double  or  two-cylinder  engine  with  crank  arms  at 
90°,  and  the  three-cylinder  engine  with  as  many  crank  arms  set  at  an 
angle  of  120°  each  with  the  other;  the  electrical  impulses  bear  just  these 
relations  with  each  other  in  the  armature  of  the  dynamo. 

The  single-phase  generators  and  motors  are  necessarily  synchronous, 


and  the  latter  are  not  self-starting,  but  must  be  brought  up  to  the  gen-  \ 

erator  speed  before  the  line  current  can  be  led  into  its  armature;  while  < 

the  polyphase  machines  are  self-starting  under  light  load,  but  not  under  ' 

full  load.                                                                                        ^                 ^  I 

It  is  evident  that  for  hoisting  and  similar  work,  where  full  load  is  ; 

thrown   on  the   machine   at   once,   alternating-current  motors  do   not  ; 

possess  the  advantages  of  direct-current  machines,  which  start  readily  I 

under  such  conditions,  and  for  short  periods  can  be  greatly  overloaded  j 

without  damage.                                                                               .  ; 

If,  therefore,  it  be  desired  to  use  electric  power  in  all  departments  of  a 

mining  plant,  the  electricity  being  generated  at  a  considerable  distance  j 

from  the  works,  cheapness  of  first  cost  and  of  copper  conductors  can  be  j 

obtained   by   using  a  high-potential   alternating  system,  with  raising  ; 

and  lowering  transformers  if  necessary;  while  by  using  rotary  trans-  j 

formers,  or  motor  generators,  as  they  are  sometimes  termed,  at  the  deliv-  | 

ery  end  of  the  line,  direct  current  can  be  obtained  for  all  work  requiring  ) 

self-starting  motors.     These  machines  used  for  transforming  alternating  i 

current  into  direct  current  at  various  potentials  have  a  common  field,  ' 
and  two  windings  upon  the  armature  revolving  within  it,  one  of  which 

receives  the  alternating  current  and  acts  as  a  motor,  while  the  other  ; 
generates  the  required  direct  current.* 

For  long-distance  transmission  the  alternating  current  possesses  the  ' 
great  advantage  of  being  convertible  from  a  low  to  a  high  potential,  or 
vice  versa,  by  means  of  a  simple  transformer,  without  moving  parts,  j 
thereby  effecting  a  great  saving  in  copper,  since,  as  already  shown,  the  \ 
greater  the  E.  M.  F.  the  less  number  of  amperes  of  current  required  to  i 
transmit  a  given  power,  and  hence  the  smaller  wire  demanded.  Single- 
phase,  alternating-current  motors,  while  not  self-starting,  may  be  heavily  i  j  j 
overloaded  without  pulling  them  out  of  synchronism  and  causing  them  \  |  't 
to  stop;  and  should  the  latter  occur,  no  damage  will  result  under  ordi-  ; 
nary  conditions,  since  the  self-induction  of  the  armature  will  hold  back 
the  current  for  several  minutes.  They  may  be  also  heavily  overloaded  jj  ; 
immediately  after  synchronizing.  The  120  horse-power  motor  in  the  u  ] 
mill  of  the  Standard  Consolidated  Mining  Company  at  Bodie,  Cal.,  has  i  : 
started  all  twenty  stamps  while  resting  upon  the  cams,  though  this,  of  ^  ' 
course,  is  not  the  ordinary  way  of  taking  up  the  load.  It  shows  that  ' 
the  motors  will  take  an  abnormally  heavy  load  at  the  outset  without  j 
damage  beyond  a  little  extra  sparking  at  the  commutator.  ; 

The  two-phase  four-wire  system  is  equally  adapted  for  both  lighting  ■ 

and  power,  and  it  is  not  necessarily  synchronous,  though  the  advantage  i 
of   speed  regulation   previously  referred   to  makes  it  advisable   to  so 

operate  the  generator  and  motor  wherever  possible.      It  will   furnish  i 

power  through   motors  of  either  the  rotating-field  type  {i.  e.,  rotating  ' 
magnetism)  or  the  polyphase;  and  by  means  of  commutating  devices 

i 

*  Induction  motors  (three-phase)  are  now  being  built  by  the  General  Electric  Com- 
pany, and  quarter-phase  machines  by  the  Westinghouse  Electric  and  Manufacturing 

Conipany,  which  it  is  claimed  are  fully  equal  in  every  respect  to  direct-current  machines.  \ 

This  is  a  development  only  to  be  expected  in  view  of  the  fact  that  the  best  electricians  { 

in  the  country  have  been  devoting  their  best  energies  to  the  attainment  of  this  most  ' 

desired  result;  and  it  will  greatly  simplify  any  quarter-phase  or  three-phase  transmis-  • 

sion  plant  where  the  power  is  to  be  used  for  the  various  classes  of  work  required  in  t 

mining.  i 


Va^^^ 


it  can  be  made  to  supply  direct  current  for  all  power  and  lighting  work 
if  so  desired,  and  at  a  very  high  efficiency  of  transformation. 

It  is  therefore  particularly  well  adapted  to  mining  requirements,  which, 
as  stated,  demand  motors  starting  immediately  and  with  full  torque  for 
certain  classes  of  work. 

"  There  are  two  especially  prominent  types  of  these  machines.  The 
first  of  these,  the  double  machine,  has  two  fields  and  two  armatures,  the 
latter  mounted  on  the  same  shaft.  Each  armature  delivers  alternating 
current  to  a  two-wire  circuit,  and  these  circuits  taken  together  consti- 
tute the  four- wire  circuit  of  the  generator;  or  they  may  be  so  connected 
as  to  constitute  a  three-wire  circuit. 

".Machines  of  the  second  type  have  single  armatures  with  two  wind- 
ings, or  with  a  single  winding  so  connected  to  the  ring  collectors  as  to 
deliver  two  currents  differing  in  their  time  relation  or  phase."* 

Twelve  machines  of  the  first  type  and  of  1,000  horse-power  capacity 
were  used  by  the  Westinghouse  Electric  and  Manufacturing  Company 
as  single-phase  generators  for  lighting  purposes  at  the  World's  Fair. 
Some  of  these  were  used  for  power  to  run  exhibit  motors,  and  in  these 
cases  were  connected  as  quarter-phase  (two-phase)  machines. 

There  is  a  decided  advantage  in  this  system  over  the  three-phase  in 
the  distribution  of  load  on  the  two  circuits  of  which  it  is  composed,  as 
the  machine  can  be  designed  to  regulate  each  current  independently, 
i.  e.,  maintain  a  constant  E.  M.  F.  with  varying  loads  on  the  circuit,  which 
cannot  be  done  with  the  three-phase  system. 

This  advantage  largely  offsets  the  saving  in  copper  of  the  latter  sys- 
tem, which  saving  can  be  put  roughly  at  about  25  per  cent  over  that  of 
either  the  single  two-wire  or  two-phase  four- wire  systems.  These  latter 
stand  on  about  an  equal  footing  as  regards  the  amount  of  copper 
required  for  transmitting  power  over  a  given  distance  at  a  stated 
potential. 

"In  a  paper  read  before  Section  *G'of  the  British  Association,  on 
September  18,  1893,  Mr.  Gilbert  Kapp  makes  the  following  statement: 
*  If  we  put  all  the  systems  on  the  same  footing  as  regards  efficiency  and 
safety  of  insulation,  we  find  the  following,  viz.:  For  the  transmission 
of  a  certain  power  over  a  given  distance  *  *  *  the  single-phase 
alternating  and  the  two-phase  four-wire  system  will  require  200  tons, 
the  two-phase  three-wire  system  will  require  290  tons,  and  the  three- 
phase  three-wire  system  only  150  tons.  As  far  as  the  line  is  concerned 
there  is  thus  a  distinct  advantage  in  the  employment  of  the  three-phase 
system.'  "f 

For  the  amounts  and  cost  of  copper  required  for  transmitting  power 
over  varying  distances  and  under  different  potentials,  the  reader  is 
referred  to  the  papers  by  Messrs.  Hasson  and  Stillwell,  already  cited. 

From  the  foregoing  it  would  appear  that  for  the  ordinary  work  of 
stamp  mills,  where  single  large  units  of  power  are  chiefly  needed,  the 
single-phase  synchronous  motors  are  well  adapted  to  meet  all  require- 
ments where  the  power  is  transmitted  from  a  distance  too  great  for  the 
use  of  the  direct  current;  while  for  a  more  extended  and  varied  use  of 


*From  "Transmission  of  Power,"  a  pamphlet  issued  by  Westinghouse  E.  &  M.  Co.,  and 
prepared  by  L.  B.  Stillwell,  E.E. 
t  "The  Electrical  Engineer"  (N.  Y.),  January  17,  1894,  p.  42. 


such  power  the  polyphase  systems  are  more  economical  and  compre- 
hensive, more  especially  the  two-phase  four-wire  method.* 

In  the  paper  by  Mr.  E.  H.  Booth,  already  referred  to,  he  speaks  of 
the  use  of  separate  motors  for  each  stamp  battery,  and  for  groups  of 
four  pans  and  two  settlers  each,  thus  doing  away  with  heavy  and 
expensive  line-shafting,  belt  alley-way,  etc. 

Such  an  extreme  subdivision  of  the  power,  however,  would  result  in 
a  heavy  loss  of  efficiency,  and  is  further  highly  impracticable  at  present 
on  account  of  the  high  speeds  at  which  electric  machines  operate,  neces- 
sitating counter  shafting  to  reduce  the  revolutions  to  the  slow  speed  of 
pan  and  cam  shafts. 

It  is  better,  therefore,  for  milling  work,  to  use  a  single  large  motor  to 
operate  the  stamps,  pans,  etc.,  with  perhaps  one  or  two  small  ones  for 
rock-crushers  and  concentrators  in  cases  where  the  cost  of  the  power  or 
the  production  of  higher-grade  concentrates  makes  this  an  object. 

The  following  description  of  the  powder-transmission  plant  of  the 
Standard  Consolidated  Mining  Company,  at  Bodie,  Cal.,  is  taken  from 
the  writer's  paper  read  before  the  American  Institute  of  Mining  Engineers 
at  the  Virginia  Beach  meeting,  February,  1894: 

THE    ELECTRIC    POWER    TRANSMISSION     PLANT     OF    THE    STANDARD    CONSOLI- 
DATED   MINING   COMPANY. 

At  Bodie,  Mono  County,  Cal.,  the  ruling  price  for  wood  has  been,  for 
years  past,  $10  per  cord,  so  that  the  monthly  fuel  bills  of  a  20-stamp  mill, 
crushing  and  amalgamating  50  tons  of  ore  per  day,  would  often  amount  to 
$2,000.  To  reduce  this  excessive  cost  of  motive  power  was  the  problem  in 
hand,  and  the  use  of  electricity  generated  by  water  power  has  solved  it. 
No  sufficient  water  power  could  be  found  nearer  than  12-^  miles,  the  dis- 
tance from  Bodie  in  a  straight  line  over  the  hills  to  the  east  flank  of  the 
Sierra  Nevada.  This  distance  is  just  at  that  intermediate  point  where 
the  cost  of  transformers  about  equals  the  difference  in  cost  between  a 
No.  1  and  a  No.  6  copper  wire  (it  is  not  advisable  to  use  any  lighter 
wire  than  No.  6,  on  account  of  its  liability  to  rupture  during  storms). 
Hence  it  was  deemed  better  not  to  use  converters,  since  they  would  only 
complicate  the  apparatus,  without  effecting  a  saving  in  cost. 

Water-Power  Plant. 

An  excellent  water  power  was  found  in  a  mountain  stream  on  the 
north  slope  of  Castle  Peak,  in  the  Sierra  Nevada,  known  as  Green  Creek, 
and  forming  one  of  the  chief  sources  of  the  East  Walker  River.  This 
stream  carries  400  in.  of  water  during  the  dry  season,  and  ten  times  that 
amount  during  the  time  of  melting  snows. 

An  old  ditch  was  cleared  out  and  rebuilt  for  a  length  of  4,570  ft.,  and 
a  site  was  selected  for  a  power-house  355  ft.  vertically  below  its  low^er 


*  For  a  full  comparison  of  the  relative  advantages  of  the  two-phase  and  the  three- 
phase  circuits,  see  "  Polyphase  Transmission,"  by  Chas.  F.  Scott,  in  the  "Electrical  Engi- 
neer "(N.  Y.),  March  21,  1894.  In  this  article  Mr.  Scott  proposes  a  combination  of  the 
two-phase  and  three-phase  systems,  generating  under  the  first  system,  and  bjr  means  of 
special  transformers  (while  also  raising  the  potential  if  so  desired)  changing  to  the 
three-phase  for  the  transmitting  line  and  again  converting  to  the  two-phase  current  at 
the  delivery  end  of  the  transmission,  thereby  uniting  the  advantages  of  saving  in  copper, 
of  the  one  system,  with  those  of  greater  simplicity,  less  cost  of  apparatus,  and  better 
regulation  of  the  other  method  (the  two-phase). 


10  — 


:y-  0?  THB     M^ 

tJHIVBRSITT] 


HEaaaH 


ELEVATION. 


Penstock   and    Flume 

Scale«-m.=  3£t: 
1893„ 


Fig.  4. 


Plan. 


/?*CZ 


g'We      () 


end.  The  ditch  was  made  larger  than  necessary  for  power  purposes 
alone,  with  the  object  of  supplying  other  parties,  when  there  was  an 
excess  of  water. 

The  maps,  Figs.  1  and  2,  give  the  data  with  regard  to  the  ditch  and 
pipe;  and  Figs.  3  and  4  show  the  connecting  flume,  pressure-tank,  and 
waste-weirs.  The  arrangement  of  the  screen  adopted,  while  it  occa- 
sions a  loss  of  head  of  a  couple  of  feet,  is  greatly  to  be  recommended 
where  "anchor"  and  slush-ice  form  in  a  ditch  during  cold  weather. 

The  pipe  is  of  large  diameter,  in  order  to  permit  subsequent  enlarge- 
ment of  the  plant,  and  also  to  reduce  loss  of  head  by  friction.  It  is 
fitted  with  three  2^  in.  air  valves,  to  prevent  collapse  in  case  of  sudden 
rupture,  and  is  anchored  at  proper  intervals  with  straps  of  li  in.  round 
iron.  The  slip-joints  extend  to  a  vertical  head  of  220  ft.,  the  remainder 
of  the  pipe  being  laid  with  collar-and-sleeve  lead  joints. 

The  pipe  leads  into  a  receiver  40  in.  in  diameter  and  9-|  ft.  long,  from 
which  four  taper-pipes  lead  the  water,  under  pressure  of  152  lbs.  per 
square  inch,  to  as  many  21  in.  Pelton  waterwheels,  each  wheel  being 
fitted  with  two  nozzles  and  rated  at  60  horse-power  under  the  largest 
sized  tips  of  1-J  in.  diameter. 

The  speed  of  the  wheels  is  860  to  870  revolutions,  and  their  shaft  is 
connected  by  an  insulated  rigid  coupling  to  the  armature  shaft  of  a  120 
K.-W.  A.  C.  generator.  Plate  I  shows  the  generator  and  waterwheels 
in  operation. 


—  12  — 

Power -House. 

The  accompanying  plan  (Fig.  5)  shows  the  arrangement  of  the  plant, 
one  of  the  most  interesting  features  of  which  is  the  water-governor  for- 
merly known  as  the  "  Doolittle,  '^  and  now  called  the  Pelton  difterential 
governor  (Figs.  6  and  7).  It  operates  butterfly- valves  placed  in  the 
Bin.  pipes  between  the  gate-valves  and  the  diverging  nozzles;  and  though 
this  form  of  valve  invariably  "throttles"  the  water  to  a  greater  or  less 


to-  ^ 


I  I  ^  I  I 


Eg 


extent  (according  to  the  position  of  the  valve),  it  is  a  most  satisfactory 
way  of  controlling  the  power  where  the  same  is  ample,  and  the  loss  due 
to  this  cause  is  of  slight  consequence.  The  governor  operates  as  follows: 
Two  18  in.  pulleys  revolve  loosely  and  in  opposite  directions  on  a  shaft, 
one  being  driven  from  the  water  wheel  shaft  and  the  other  by  a  No.  2 


—  13  — 

Pelton  motor.  These  pulleys  have  gears  on  their  hubs  which  mesh  into 
two  other  gear-wheels  carried  on  an  axis  at  right  angles  to  the  shaft  and 
keyed  fast  to  the  latter.  Beyond  these  wheels  is  a  pinion,  loose  on  the 
shaft  and  with  ratchet-teeth  cut  in  opposite  directions  on  either  side  of 
its  hub.  Into  these  ratchet-teeth  mesh  corresponding  circular  ratchets, 
which  are  keyed  to  the  shaft  but  free  to  move  longitudinally  along  the 
same,  and  are  thrown  in  or  out  of  gear  by  a  short  lever  and  spring. 
The  pinion  engages  a  sector,  which  is  fastened  to  the  rod  and  levers  that 
operate  the  butterfly-valves,  and  on  the  same  rod  is  a  hand-lever,  by 
means  of  which  the  valves  may  also  be  opened  or  closed  by  simply  throw- 


End  Elevation  of  Water  Wheels. 

Scale  1  in.—  3  ft. 

ing  out  of  mesh  the  circular  ratchets  alluded  to  and  thereby  detaching 
the  governor.  It  is  evident  that  when  the  two  pulleys  are  revolving  in 
opposite  directions  at  exactly  the  same  rate  of  speed,  there  will  be  no 
motion  of  the  central  gear-shaft,  and  none  will  be  communicated  to  the 
pinion  and  sector  and  thence  to  the  valves,  to  open  or  close  them;  while, 
on  the  other  hand,  a  difference  in  speed  of  these  pulleys  will  have  the 
opposite  effect.  The  belts  driving  them  are  therefore  so  arranged  that 
a  decrease  in  speed  of  the  waterwheels  will  open  the  valves,  and  an 
increase  will  close  them. 

In  starting  up  from  rest,  the  governor  is  detached  by  throwing  out  the 
springs  on  the  ratchets,  and  the  valves  are  operated  by  the  hand-lever. 


—  14  — 

After  the  wheels  are  at  normal  speed  and  the  load  is  on,  the  ratchets  are 
sprung  into  gear  with  the  pinion,  and  the  governor  takes  care  of  any 
and  all  variations,  even  to  a  complete  throwing  off  of  the  load  by  pull- 
ing the  main-current  plug-switch  at  Bodie.  The  speed  of  the  governor- 
pulleys,  as  first  designed,  was  60  revolutions.  This  was  found  to  be  too 
slow,  and  it  was  increased  to  180  revolutions  with  most  beneficial  effects, 
developing  a  greater  sensitiveness  to  small  changes  of  load,  and  much 
quicker  action,  especially  when  all  the  load  was  thrown  off' at  once.  In 
the  latter  case,  the  increase  in  speed  of  the  waterwheels  did  not  at  any 
time  exceed  12  per  cent  before  the  governor  began  to  close  the  valves. 

It  was  further  found  necessary  to  furnish  a  constant  resistance  for  the 
water  motor  that  drives  one  side  of  the  governor,  to  work  against.  In 
the  original  plan  this  was  to  be  done  by  the  exciter  which  furnishes  cur- 
rent for  the  fields  of  the  generator;  but  on  trial  it  appeared  that  the  load 
on  the  exciter  was  too  variable,  and  at  times  too  great  for  the  little 
motor  to  take  care  of.  The  exciter  was  then  placed  so  that  it  could  be 
driven  by  either  a  larger  size  (No.  3)  motor  or  by  the  water  wheel  shaft- 
coupling  (see  plan  of  power-house);  and  a  fly-wheel  of  about  1,500  lbs. 
weight  was  set  to  be  driven  by  the  smaller  motor  and  insure  its  constant 
speed. 

The  great  drawback  to  the  use  of  water  power  for  the  generation  of 
electricity  has  hitherto  been  the  lack  of  a  good  water-governor,  sufficiently 
sensitive  and  quick-acting  to  insure  the  vital  factor  of  constant  speed 
without  bringing  dangerous  strain  on  the  water  pipe.  In  fact,  in  the 
Westinghouse  plant  at  Telluride,  and  in  several  others  of  which  the 
writer  is  aware,  the  "one-man  automatic  regulator"  had  to  be  used;  i.  e., 
a  man  sat  with  his  hand  on  the  lever  of  a  deflecting  nozzle  and  his  eye 
fixed  on  a  voltmeter  or  a  techometer.  The  above-described  governor  is 
so  great  an  improvement  over  this  system  that  its  operation  has  been 
given  in  detail. 

The  generator  is  a  Westinghouse  120  K.-W.  constant-potential  twelve- 
pole  machine,  and  its  armature-shaft  is  attached  to  that  of  the  water- 
wheels  by  a  rigid  coupling,  insulated  by  a  disk  of  hard  rubber  one  inch 
thick,  and  projecting  one  inch  beyond  the  flanges,  while  the  bolts  are 
surrounded  by  bushings  and  washers  of  insulating-fiber. 

The  initial  current  in  the  lower  half  of  each  field-coil,  or  the  winding 
nearest  the  armature,  is  instilled  by  means  of  a  type  "G''  D.  C.  exciter. 
The  secondary  winding,  on  the  armatiire-spokes  of  the  dynamo, 
generates  current  when  the  machine  is  under  load,  which  is  led  to  a 
twelve-bar  commutator  on  the  armature-shaft  and  thence  to  the  com- 
pensating-winding  which  occupies  the  upper  half  of  each  field-bobbin. 

As  the  load  on  the  generator  increases,  more  current  flows  through  its 
armature-coils,  and  through  a  primary  winding  on  the  armature-spokes, 
thereby  inducing,  in  the  secondary  winding,  a  heavier  current,  which, 
being  led  to  the  magnetic  field  as  described,  proportionately  strengthens 
the  same.  When  the  generator  is  running  without  load,  there  being 
little  or  no  current  in  its  armature-coils,  none  is  induced  in  the  second- 
ary winding,  and  the  compensating- winding  on  the  fields  is  without 
magnetic  effect  until  the  latter  is  required  by  work  to  be  performed. 

The  potential  of  the  generator  under  full  load  is  3,530  volts,  but  at 
present  it  is  operating  with  about  3,390.  The  exciter  carries  a  voltage 
of  105  to  112.  A  "D.  C."  voltmeter,  recently  placed  on  the  switch-board 
to  the  left  of  the  ground-detector  and  above  the  small  rheostat,  is  in  the 


sis 


SB 

o 


UKIVBRSIT 


-  15  -  ^^J-T^^^^^ 

main  circuit  of  the  exciter,  recording  the  tension  of  its  current. and 
serving  as  a  speed  indicator  when  the  machine  is  driven  by  the  N6.  o 
motor.  This  is  not  necessary  when  driving  from  the  wheel-shaft,  as  is 
sometimes  done  in  winter,  when  pieces  of  ice  give  trouble  in  the  small 
nozzle  of  the  motor. 

Plate  II  shows  the  generator  switch-board  at  the  power-house.  The 
generator  current  is  led  from  the  collector-rings  on  the  extreme  end  of 
the  armature-shaft  to  the  plug-sockets  on  the  switch-board;  and  when 
the  line-plugs  are  in  these,  the  current  follows  the  line  to  two  similar 
sockets  on  the  motor  switch-board.  The  small  converter  in  the  upper 
middle  of  the  switch-board  has  a  transforming  ratio  of  80  to  1.  Its 
primary  coil  is  attached  to  the  main-current  wires  from  the  generator, 
and  its  secondary  to  the  A.  C.  voltmeter,  immediately  below  it.  A 
potential  of  113  volts  on  the  voltmeter  is  therefore  equivalent  to  3,390 
on  the  dynamo  current,  which  is  the  tension  under  normal  load.  The 
voltmeter  does  not,  however,  read  113  volts,  but  records  100  to  102  volts, 
the  difference  being  due  to  the  compensator  (the  instrument  shown  in  . 
the  upper  left-hand  corner  of  the  switch-board  and  connected  with  the 
voltmeter),  the  object  being  to  reduce  the  reading  by  an  amount  about 
equal  to  the  line-loss.  This  loss  is  estimated  at  15  per  cent  under 
maximum  load,  and  is  but  from  8  to  10  per  cent  under  normal  load, 
as  will  be  shown  later  on. 

The  ammeter,  and  just  below  it  the  aluminum  fuses,  all  of  which  are 
in  the  main  circuit,  are  shown  to  the  left  of  the  voltmeter  in  the  view  of 
the  generator  switch-board. 

Immediately  to  the  left  of  the  main-line  plug-switches  is  the  ground- 
detector  with  two  lamps,  one  for  each  leg  of  the  line,  and  each  lamp 
with  its  converter  behind  it. 

A  press-button  below  the  lamps  makes  the  necessary  connection  with 
a  ground  wire.  Without  this  connection  made,  the  lamps  sho-w  a  red 
light  on  the  filaments,  due  to  the  difference  in  potential  of  the  two  sides 
of  the  line;  and  should  a  "  ground  "  occur  on  either  leg  of  the  wire-line, 
the  corresponding  lamp  immediately  burns  at  full  candle  power,  while 
the  other  lamp  proportionately  diminishes. 

The  two-pole  jaw-switch  to  the  left  of  the  switch-board  is  in  the  circuit 
from  the  exciter  to  the  generator-fields,  as  are  also  the  two  fuses  and  the 
rheostat  immediately  below  it.  The  small  rheostat  to  the  right  of  the 
fuse-blocks  and  the  single-pole  switch  below  it  are  in  the  shunt  field- 
circuit  of  the  exciter.  By  means  of  these  two  rheostats  the  potential  of 
the  generator  is  governed  and  the  voltmeter  kept  at  its  proper  reading, 
the  large  rheostat  in  the  exciter  and  generator  field-circuit  permitting  a 
quick  regulation  over  a  wide  range,  and  the  shunt-rheostat  a  finer  and 
closer  adjustment  of  the  voltage. 

When  starting  up  the  plant  one  attendant  stands  at  the  lever,  con- 
trolling the  admission  of  water  to  the  wheels  through  the  butterfly-valves, 
and  the  other  at  the  switch-board,  handling  these  two  rheostats  (most 
of  the  regulation  is  done  by  the  large  one),  until  the  motor  is  in  syn- 
chronism and  at  work,  when  the  governor  is  thrown  into  gear,  the  voltage 
is  finally  adjusted,  and  the  mechanism  is  then  practically  self-regulating 
for  all  ordinary  changes  of  load.  If,  for  instance,  ten  of  the  twenty 
stamps  are  to  be  hung  up,  or  any  or  all  of  the  eight  continuous-pans  in 
the  mill  are  to  be  stopped,  it  is  never  necessary  first  to  give  word  to  the 
attendant   at   the   power-house.     The   governor  takes   charge  of   such 


—  16  — 

changes,  even  to  the  entire  throwing  off  of  the  load,  as  before  remarked. 
All  the  bearings  of  the  generator  and  waterwheel  shafts  and  of  the 
exciter  are  self-oiling.  The  attendant  has  merely  to  keep  on  the  qui  vive 
and  see  that  all  is  running  smoothly.  Any  change  in  tone  of  the  hum 
of  the  dynamo  warns  him  at  once  of  a  change  of  conditions,  the  tone 
rising  or  falling  according  as  the  speed  increases  or  diminishes,  though 
ever  so  slightly. 

To  insure  the  all-important  factor  of  constant  speed,  a  techometer, 
registering  to  1,200  revolutions,  is  belted  to  the  waterwheel  and  dynamo 
shaft.  Its  dial  faces  the  waterwheels,  so  that  the  attendant  at  the  valve 
lever  can  readily  maintain  a  uniform  speed  during  the  operation  of 
"synchronizing"  the  motor  and  starting  the  mill,  at  which  time  the 
load  is  constantly  varying. 

In  front  of  the  jaw-switch  on  the  switch-board  there  will  be  noticed, 
in  the  view  of  the  latter,  a  steel  spring,  and  also  two  cords  attached  to 
the  handle  of  the  large  rheostat.  These  cords  are  led-  around  the  side 
of  the  building  to  the  attendant's  place  at  the  valve-lever,  as  is  also  the 
one  that  releases  the  catch  of  the  spring.  A  pull  on  these  cords  opens 
the  exciter  main-circuit  instantly,  and  puts  in  the  entire  resistance-box, 
thereby  "  killing"  the  fields  of  the  generator  and  preventing  any  danger- 
ous rise  in  electro-motive  force,  should  the  load  be  suddenly  thrown  ofl' 
by  a  break  in  the  wire-line,  or  other  accident  causing  a  sudden  increase 
in  the  speed  of  the  armature  shaft.  It  should  be  explained  that  this 
arrangement  was  devised  by  the  writer,  before  the  speed  of  the  governor 
was  trebled,  the  constant-resistance  fly-wheel  was  put  in  and  other 
changes  were  made,  giving  more  sensitive  and  perfect  control  of  the 
water  power;  and  it  is  left  in  place  because  it  might  still  be  of  use  in 
case  of  emergency.  The  power-house  is  lit  by  a  small  10-light  converter 
attached  to  the  generator-circuit,  and  when  the  generator  is  not  in  opera- 
tion, by  current  from  the  exciter.  Plate  III  shows  the  power-house  at 
Green  Creek. 

Wire-Line. 

The  length  of  the  line  is  67,760  ft.,  or  12.46  miles.  The  poles  are  of 
round  tamarack  timber,  21  ft.  long,  6  in.  in  diameter  at  the  top,  set 
4  ft.  in  the  ground;  poles  25  ft.  long  being  used  through  the  town,  and 
along  the  line  wherever  there  is  danger  of  deep  snowdrifts.  They  are 
placed  100  ft.  apart,  and  fitted  each  with  a  4  by  6  in.  cross-arm,  boxed 
into  the  pole,  and  held  by  one  bolt  and  one  lag-screw\  The  accompany- 
ing sketch  (Fig.  8)  shows  the  detail.  The  object  of  chamfering  the  ends 
of  the  cross-arms  is  to  leave  less  room  for  the  lodging  of  snow  under  the 
insulator. 

The  line  crosses  extremely  rough  country,  not  500  yds.  of  which  is 
level  beyond  the  town  limits.  Most  of  the  ground  is  very  rocky,  over 
500  lbs.  of  dynamite  being  used  in  blasting  the  pole-holes.  Plates  IV 
and  V  are  views  along  the  line  in  summer. 

The  wire  is  of  No.  1  (B.  &  S.)  gauge,  soft-drawn  bare  copper,  and  is 
attached  to  standard,  double-petticoat,  deep-groove  glass  insulators  (Fig. 
10)  carried  on  Klein  patent  iron  pins  (Fig.  9).  The  distance  between 
the  wires  is  3  ft.  8  in.,  and  there  are  over  16.5  tons  of  copper  in  the  line. 
The  only  objection  found  to  the  iron  pins  is  their  liability  to  be  with- 
drawn from  the  cross-arm  during  a  gale  of  wind,  whenever  there  is  an 
upward  pull  on  the  wire.     To  obviate  this  a  number  of  pins  were  drilled 


T72ri7ERSIT7^ 


'■'-'''■i?- 


J 


'  '^'^^^Rin.^ 


UHI7BRSITT] 


—  17  — 


-3-  8-between:  Wires 


J 

s          *%    V 

)  ■ 

'           ^'     1 

i       !    \       I 

1   r\  ^ 
1^  >    \ 

DEEP  GROOVE  Double-Petticoat 
Glass  Insulator.      Half  Size. 


Westinghouse   "Pomona"  Double-Petticoat 
Glass  Insulator.      Half  Size. 

Line    Details. 


—  18  — 

with  an  -J  in.  hole  near  the  end,  and  in  all  such  places  these  were  used, 
and  held  firm  by  driving  a  wire  nail  through  them. 

The  wire  was  first  attached  to  the  insulators  by  tie-wires  of  No.  10 
galvanized  iron  wire.  Later  it  was  found  advisable  to  insulate  the  line- 
wire  at  the  insulators,  and  for  this  purpose  ordinary  sheet-rubber  -^  in. 
thick,  such  as  is  used  for  gaskets,  was  cut  into  strips  1.5  in.  wide  and 
12  in.  long.  These  were  wound  spirally  about  the  wire  and  held  in 
place  by  two  close  wrappings  of  Hanson's  tape.  The  whole  was  then 
well  daubed  with  asphalt  paint,  and  the  insulated  wire  re-attached  to 
the  insulators  by  tie-wires  of  No.  6  weather-proof  copper  wire. 

The  line  crosses  a  number  of  very  steep  ridges  (from  300  to  800  ft.  in 
height),  and  on  these  the  wire  necessarily  pulls  heavily  on  the  top  pole, 
and  especially  on  its  pins  and  insulators.  In  all  such  places  the  ordi- 
nary double-petticoat  insulators  were  replaced  by  the  large  "Pomona" 
insulator  (Fig.  11),  on  which  the  wire  is  carried  in  a  groove  across  the 
top,  and  its  weight  is  therefore  directly  down  upon  and  in  line  with  the 
center  of  the  pin. 


Fig.  12. 

Pole  No.  40;  4,000  ft.  from  Mill. 
(Wire  is  17  ft.  above  ground  at  pole.    Snow-drift  15  ft.  deep,  March,  1893.) 

The  line  has  given  no  trouble  whatsoever,  and  has  carried  the  high 
potential  of  3,000  volts  without  a  leak,  even  during  a  severe  storm  of  ten 
hours'  duration,  the  rain  changing  to  sleet  and  ice  toward  the  end;  but 
this  severe  test,  it  must  be  admitted,  occurred  after  the  wire  had  been 
wrapped  at  the  insulators  as  described.  In  fact,  one  of  the  chief  objects 
of  this  insulation  was  to  render  the  line  proof  against  just  such  a  storm 
as  this.     Snow-storms  have  no  effect  whatever.     (See  Fig.  12.) 

Motor-Room. 

The  motor  that  drives  the  stamp  mill  of  the  Standard  Consolidated 
Mining  Company  at  Bodie  is  an  A.  C.  synchronous  constant-potential 
machine  of  120  horse-power.  The  mill  contains  twenty  750  lb.  stamps, 
four  wide-belt  (6  ft.)  Frue  vanners,  eight  continuous-process  amalga- 
mating-pans  (two  of  which  are  constantly  grinding),  three  settlers,  one 


!    ] 


^f  .'f 


Plate  VII.     Motor  Switch-Board. 


^s^ 


v 


^3^ 


£4LIfOt3 


—  19  — 

agitator,  one  pan  and  settler  devoted  to  the  amalgamation  of  concen- 
trates, a  bucket  elevator,  a  worm-gear  hoist,  and  a  rock-crusher.  In 
order  to  determine  accurately  the  capacity  of  motor  required,  a  number 
of  cards  were  taken  with  the  Tabor  indicator  from  the  20  by  36  inch 
steam  engine  that  drove  the  mill,  showing  an  average  of  90  and  a  maxi- 
mum of  101^  horse-power. 

The  fields  of  the  motor  are  self-exciting  through  a  secondary  winding 
on  the  teeth  of  the  armature,  the  current  being  led  to  a  twelve-bar  com- 
mutator similar  to  that  on  the  generator.  In  fact,  the  motor  is  almost 
identical  with  the  generator,  the  chief  difference  being  in  the  compensat- 
ing-winding  on  the  field-bobbins  of  the  latter. 

On  the  armature-shaft  of  the  motor  is  a  friction-wheel,  and  beyond 
this  a  clutch,  which  is  used  to  set  in  motion  the  driving-pulley  and  the 
machinery  of  the  mill.  On  the  same  bed-plate  with  the  motor  is  a  small 
10  horse-power  Tesla  starting-motor,  with  a  wooden  pulley  on  its  shaft, 
that  is  brought  to  bear  against  the  friction-wheel  mentioned,  by  means 
of  a  screw  and  hand-wheel.  This  Tesla  motor  consists  simply  of  field- 
coils  and  an  armature;  it  has  neither  brushes,  nor  commutator,  nor 
sliding  contacts  of  any  kind.  The  alternating  current  is  led  directly  into 
the  fields,  the  stationary  element,  the  coils  of  which,  being  connected  in 
series,  produce  a  rotating  magnetic  field,  in  that  each  pole  is  alternately 
positive  and  negative.  The  starting-torque  of  the  armature  is,  in  conse- 
quence, very  low,  and  it  has  to  receive  several  rapid  turns  by  hand 
before  putting  on  the  current,  after  which  it  generally  runs  up  to  normal 
speed  (1,660  revolutions)  within  a  minute.  Plate  VI  shows  the  motor 
in  operation. 

Turning  our  attention  to  the  switch-board,  shown  in  Plate  VII,  the 
two  plugs  in  the  sockets  on  the  right  of  the  board  are  the  line-plugs, 
and  the  two  to  the  left  of  them,  in  their  rests,  are  the  starting-motor 
plugs.  When  the  line-plugs  are  in  their  sockets  the  current  is  led 
directly  to  the  top  of  the  upper  jaw-switch,  and  this  switch  is  never 
closed  until  the  machines  are  in  synchronism.  The  wires  from  the 
bottom  of  this  switch  lead  directly  to  the  collector-rings  on  the 
armature-shaft  of  the  motor. 

In  the  upper  right-hand  of  the  board  is  the  Wurts  lightning-arrester, 
consisting  of  22  spools,  1 1  on  a  side,  separated  each  by  a  distance  of  -^^  in. 
Both  legs  of  the  wire-line  are  attached  to  the  arrester,  one  on  each 
side  at  the  top,  while  the  ground-wire  leads  from  the  bottom  spools  to 
a  water-pipe  in  the  earth.  The  spools  are  made  of  a  patent  non-arcing 
metal,  and  the  dynamo  current  will  therefore  not  follow  the  path  through 
them  made  by  a  discharge  of  high-tension  atmospheric  electricity.  The 
properties  of  this  alloy  are  such  that  oxides  of  the  metals  are  generated 
by  the  passage  of  lightning  and  not  vapor  of  the  metal  itself. 

To  the  left  of  this  instrument  are  two  converters  of  the  ratio  of  30  to 
1,  filled  with  paraffine  oil.  The  primary  coil  of  the  right-hand  one  is 
connected  to  the  main  line  just  above  the  plug-sockets,  and  that  of  the 
left-hand  converter  is  connected  to  the  motor-circuit,  i.  e.,  the  wires 
leading  from  the  collector-rings  on  the  armature-shaft  to  the  bottom  of 
the  upper  jaw-switch;  it  being  understood  that  the  motor  acts  as  a 
generator  when  being  driven  by  the  starting-motor. 

The  secondary  of  the  line-current  converter  goes  to  the  top  posts, 
marked  G,  of  the  synchronizer  (the  marble  plate  with  four  lamps  on  it 
to  the  extreme  left  of  the  board),  one  leg  being  first  carried  through  the 


—  20  — 

right-hand  side  of  the  lower  jaw-switch.  When  the  line-plugs  are  in, 
therefore,  and  this  switch  is  closed,  the  top  light  of  the  synchronizer 
will  always  be  burning  while  the  generator  at  the  power-house  is  in 
operation. 

The  secondary  of  the  motor-current  converter  is  carried  directly  to 
the  bottom  posts,  marked  M,  of  the  synchronizer,  the  two  middle  lamps 
of  which  are  connected  in  series  with  the  motor  and  generator  currents. 
.  The  field-circuit  of  the  motor  is  carried  to  the  switch-board,  and  in  it 
are  placed  the  large  rheostat,  the  left-hand  ammeter,  and  the  left-hand 
side  of  the  lower  jaw-switch.  The  closing  of  this  switch  and  an  adjust- 
ment of  the  rheostat  will  therefore  cause  the  lower  light  on  the  syn- 
chronizer to  burn  whenever  the  motor  is  being  run  as  a  generator,  as  is 
the  case  when  it  is  being  driven  by  the  starting-motor.  The  aluminum 
fuses  showing  below  the  converters  are  in  the  main  line  before  it  reaches 
the  jaw-switch,  as  is  also  the  ammeter  just  below  them,  which  instru- 
ment should,  and  does,  record  the  same  volume  of  current  as  its  fellow 
in  the  power-house. 

To  start  the  motor  requires  two  men,  one  to  handle  the  starting- 
motor  and  the  other  at  the  switch-board.  The  line-plugs  are  put  in, 
which  leads  the  main  current  to  the  top  of  the  synchronizing-s witch, 
and  the  lower  jaw-switch  is  thrown  in,  which  closes  the  field-circuit  of 
the  motor,  and  the  secondary  of  the  main-line  or  generator  converter, 
thereby  lighting  the  upper  lamp  of  the  synchronizer.  The  armature  of 
the  starting-motor  is  turned  a  few  times  by  hand,  and  the  two  left-hand 
plugs  are  then  pushed  into  their  sockets,  leading  the  current  from  the 
main  line  to  the  fields  of  this  motor. 

Immediately  upon  doing  this,  the  main-current  ammeter  records  30 
amperes,  and  the  needle  stays  at  this  reading  until  the  starting-motor 
is  up  to  speed,  when  it  drops  quickly  to  18  to  20  amperes.  It  takes  from 
fifty  to  seventy  seconds  for  the  starting-motor  to  reach  full  speed,  after 
which  its  friction-wheel  is  brought  to  bear  against  that  of  the  main 
motor,  and  the  armature  of  the  latter  begins  to  revolve.  During  this 
time  the  synchronizing-switch  (the  upper  jaw-switch)  is  open,  and  all 
the  resistance-coils  of  the  rheostat  are  left  in  the  field-circuit,  in  order 
that  the  armature  may  more  easily  be  brought  up  to  speed,  by  prevent- 
ing the  flow  of  current  in  the  same. 

As  soon  as  the  armature  is  above  speed,  about  two  thirds  of  the 
rheostat  is  thrown  out,  permitting  40  or  50  amperes  of  current  to  flow, 
and  the  lower  lamp  of  the  synchronizer  to  burn.  The  pushing  onto  its 
button  of  the  little  switch  on  the  bottom  of  the  synchronizer  now  con- 
nects the  two  central  lamps  in  series  with  the  motor-  and  the  generator* 
currents,  and  they  begin  to  flash  in  accordance  with  the  phases,  and 
therefore  the  speeds,  of  the  two  machines.  As  the  speed  of  the  motor 
approaches  that  of  the  generator,  the  wave-phases  come  nearer  coinci- 
dence, and  these  lamps  brighten  and  darken  almost  simultaneously. 

The  attendant  stands  with  one  hand  on  the  rheostat  and  the  other 
on  the  open  jaw-switch,  watching  these  waves  of  light  intently,  and  just 
as  the  two  lamps  darken  in  unison,  he  throws  in  the  switch  and  pulls 
one  of  the  starting-motor  plugs.  The  lamps  only  remain  "out"  for  a 
second  or  less,  while  the  speeds  are  together,  and  then  flash  up  brightly 
again  as  the  motor  speed  drops  off;  there  is  therefore  but  a  fraction  of  a 
second  during  which  the  jaw-switch  should  be  closed,  though  this  time 
can  be  lengthened  slightly  by  a  proper  handling  of  the  starting-motor. 


—  21  — 

If  this  switch  has  been  thrown  in  at  the  right  moment,  the  series 
lights  remain  "out,"  while  the  top  and  bottom,  or  "pilot''  lights,  burn 
brightly,  and  so  continue  all  the  while  the  machines  are  in  operation. 

If  the  switch  is  thrown  in  a  second  or  so  too  soon,  the  main-current 
ammeter  will  fly  up  to  40  or  46  amperes,  and  quickly  drop  down  to  less 
than  10  as  the  motor  speed  decreases,  and  it  falls  into  step  with  the 
generator,  while  the  series-lamps  will  remain  dark,  and  the  pilot-lamps 
burn  as  usual.  On  the  other  hand,  if  it  is  closed  several  seconds  too 
soon,  or  a  fraction  of  a  second  too  late,  it  is  impossible  for  the  machines 
to  get  into  synchronism.  In  such  event  all  the  lights  on  the  syn- 
chronizer go  out  at  once,  and  a  heavy  flow  of  current  sets  in,  the  main 
ammeter  showing  45  amperes,  which  is  as  high  as  it  can  record.  By  the 
extinction  of  the  lights  the  attendant  sees  at  once  that  he  has  missed 
the  synchronizing-point,  and  immediately  pulls  the  main-line  plug, 
opens  the  jaw-switch,  and  starts  over  again.  The  second  trial,  however, 
will  not  consume  as  much  time  as  the  first,  since  the  starting-motor  is 
still  revolving  at  a  high  speed,  and  more  quickly  comes  up  to  its  normal 
rate,  while  the  motor-armature  is  also  running  yet  at  several  hundred 
revolutions  per  minute. 

This  very  rarely  happens,  especially  since  the  addition  in  March  last 
of  an  acoustic  synchronizer  to  the  phase-lamp  device.  This  instrument 
emits  a  sound,  the  pulsations  of  which  are  very  rapid  at  first,  the  inter- 
val between  them  .growing  longer  as  the  machines  approach  equal  speed, 
and  settling  into  a  steady  hum  at  the  moment  of  synchronism. 

It  will  be  noticed  that  in  order  to  break  the  circuit  and  stop  the  motor 
it  is  necessary  to  pull  the  line-plug,  on  doing  which  a  brilliant  arc, 
sometimes  2  ft.  in  length,  if  25  amperes  are  flowing,  follows  out  from  the 
socket  to  the  plug-tip.  Any  attempt  to  open  the  jaw-switch  while  the 
line-plugs  are  in  would  doubtless  result  in  the  death  of  whomsoever  tried 
it,  since  the  distance  is  too  short  in  which  to  break  the  arc,  and  the  cur- 
rent would  likely  follow  down  the  arm  in  spite  of  one's  standing  on  an 
insulated  floor.  These  floors  are  used  around  both  generator  and  motor, 
and  in  front  of  both  switch-boards. 

The  entire  operation  of  starting  up  the  motor  from  a  state  of  rest 
occupies  from  three  to  five  minutes,  and  when  once  in  synchronism,  the 
clutch  can  be  thrown  in  and  the  mill  shafting  brought  to  normal  speed 
in  from  one  to  two  minutes  more,  after  which  the  load  may  be  thrown 
on  as  fast  as  desired  without  the  least  danger  of  pulling  the  motor  out 
of  synchronism.  The  clutch  is  always  thrown  in  slowly  in  order  to 
prevent  too  heavy  a  flow  of  current,  and  consequent  sparking  of  the 
commutator  brushes. 

By  means  of  a  single  counter-shaft,  fitted  with  self-oiling  boxes,  the 
high  speed  of  the  motor  (860  revolutions)  is  reduced  to  the  necessary  80 
revolutions  of  the  battery  line-shaft,  the  reductions  being  2  ft.  to  8  ft., 
and  3  ft.  to  8  ft.  Light  steel-rim  balanced  pulleys  are  used,  and  an 
endless  16  in.  double  leather  belt  runs  from  the  motor  to  the  first  8  ft. 
pulley.  The  speed  of  this  belt  is  5,400  ft.  per  minute,  and  it  is  kept 
tight  by  levers  which,  acting  through  screws,  move  the  entire  motor  and 
its  bed-plate  along  four  grooved,  cast-iron  slides. 

The  motor  is  separated  from  the  underlying  brick  foundation  by 
means  of  8  by  10  in.  timbers,  which  are  bolted  to  the  latter  and  covered 
by  three  layers  of  1  in.  boards;  and  to  this  wood  insulation  the  slides 
referred  to  are  fastened  by  lag-screws  that  pass  through  the  boM^s^ 

^f^^  0?  THl 


1^ 


—  22  — 

the  timbers.  The  generator  is  insulated  from  the  I-beams  that  carry- 
both  it  and  the  waterwheels,  by  timbers  5^  in.  thick,  to  which  it  is  like- 
wise secured  by  lag-screws. 

The  mill  and  offices  of  the  company  are  lit  by  100- volt  incandescent 
lamps,  taking  current  from  a  large  100-light  converter,  ratio  30  to  1, 
which  is  attached  to  the  main  line  in  the  motor-room,  before  it  reaches 
the  switch-board.  The  light  is  very  satisfactory,  even  to  read  or  write 
by,  although  at  times  the  lamps  flicker  slightly,  due  to  small  changes 
of  load.  This  variation  of  intensity  is,  of  course,  unavoidable  where  the 
lighting  current  is  taken  direct  from  a  power  circuit;  but,  in  the  present 
case  at  least,  is  not  sufficiently  noticeable  to  cause  inconvenience. 

During  normal  operation  of  the  plant,  the  field-ammeter  of  the  motor 
is,  by  means  of  the  rheostat,  kept  steadily  at  52  amperes,  while  with  full 
load  on  the  mill  the  main-current  ammeter  registers  from  23  to  25 
amperes.  The  needle  oscillates  over  a  range  of  4  to  6  amperes,  showing 
considerable  variation  of  load,  due  undoubtedly  to  slipping  of  the  belts, 
unequal  resistance  of  the  grinding-pans,  rock-crusher,  etc.,  so  that  it  is 
difficult  to  read  this  ammeter  closely,  either  at  the  generator  or  at  the 
motor. 

The  average  amperes  of  current  can  be  very  closely  approximated, 
however,  as  was  done  in  the  tabulated  readings  given  below,  which  were 
taken  with  the  object  of  determining  the  line-loss,  and  with  the  aid  of 
Mr.  H.  M.  Reed,  the  engineer  of  the  Westinghouse  Electric  and  Manu- 
facturing Company,  who  installed  and  first  operated  this  apparatus. 

The  readings  were  taken  simultaneously  at  power-house  and  motor- 
room,  by  means  of  the  telephone,  and  the  figures  given  are  the  averages 
of  five  or  six  consecutive  observations.  There  being  no  voltmeter  on 
the  motor  switch-board,  a  Weston  portable  voltmeter  was  used,  the 
wires  being  attached  to  the  lower  posts  on  the  synchronizer. 

The  table  is  merely  a  rough  approximation  of  the  efficiency  of  the 
transmission,  there  being  no  instruments  at  hand  for  close  work,  such 
as  the  measurement  of  the  wheel-shaft  energy,  or  of  that  given  out  at 
the  motor-pulley.  The  efficiency  of  these  machines,  namely,  of  the  gen- 
erator, 95.5  per  cent,  and  of  the. motor,  93.9  per  cent,  was  determined  by 
Mr.  Fred.  A.  Davis,  electrical  engineer  of  the  Westinghouse  Electric  and 
Manufacturing  Company,  in  charge  of  the  plant.  It  will  be  noticed 
from  the  table  that  the  line-loss  is  very  light,  and  also  that  as  the 
dynamo  and  motor  approach  their  rated  capacity,  the  efficiency  of  the 
transmission  increases. 


—  23 


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—  24  — 

The  proper  setting  of  the  brushes  on  the  commutator  of  the  motor- 
armature  is  a  knack  acquired  only  by  experience;  and  for  awhile  con- 
siderable trouble  was  caused  by  undue  sparking  at  these  brushes. 
Experience  on  the  part  of  the  attendants  has  entirely  overcome  this; 
but  it  has  been  found  necessary  to  use  two  commutators,  keeping  one 
always  turned  and  polished  ready  for  use,  and  changing  them  usually 
after  twenty-five  to  thirty  days  of  steady  operation. 

In  order  to  stop  the  motor,  the  load  is  thrown  off  by  means  of  the 
clutch,  and  the  line-plug  is  then  pulled.  Should  the  plug  be  pulled 
without  first  throwing  off  the  load,  a  momentary  rise  in  electro-motive 
force  may  follow,  sufficient  to  damage  an  armature-coil.  This  has  hap- 
pened once  in  our  experience,  and  the  very  high  potential  was  vividly 
shown  by  the  discharge  through  the  lightning-arresters  at  both  ends  of 
the  line. 

The  dependence  of  the  motor  speed  upon  the  alternations  of  the 
generator  is  very  prettily  shown,  when,  without  pulling  the  line-plugs, 
the  machines  are  stopped  by  shutting  oflt'  the  water  on  the  wheels.  The 
motor  then  slows  down  in  exact  accordance  with  the  generator,  and  is 
at  rest  within  half  a  minute  or  so;  whereas,  when  the  plug  is  pulled  in 
the  usual  way,  the  motor-armature  will  revolve  for  several  minutes 
from  its  own  momentum  before  coming  to  a  stop. 

This  plant  has  accomplished  several  unbroken  runs,  day  and  night,. 
one  of  thirteen  days'  and  another  of  twenty  days'  duration,  but  latterly 
it  has  been  operated  more  intermittently,  on  account  of  the  mill  being 
run  upon  only  half-time.  During  December,  1893,  the  plant  was  started 
twenty-three  times  in  twenty-one  days,  and  in  January  eleven  times  in 
as  many  days  (in  accordance  with  the  requirements  of  the  milling  work), 
these  daily  startings  being  an  excellent  test  on  both  the  starting-motor 
and  machines,  as  at  such  times  the  differences  in  potential,  and  conse- 
quently the  strain  on  the  insulation,  are  likely  to  be  a  maximum. 

The  only  trouble  now  experienced  with  the  plant  comes  from  an 
extraneous  source,  common,  in  a  greater  or  less  degree,  to  all  electrical 
plants  throughout  the  world,  namely,  occasional  incursions  of  lightning 
during  thunder-storms;  or  from  another,  more  local  cause,  already 
alluded  to,  namely,  discharges  of  static  electricity,  due  to  a  gradual 
charging  of  the  line  from  a  highly  charged  atmosphere  during  wind- 
storms. These  have  several  times  caused  the  burning-out  of  armature- 
coils;  but  this  matter  is  not  as  serious  as  it  may  seem,  since  but  a  couple 
of  hours  are  required  to  repair  such  damage.  To  put  in  a  new  coil,  the 
top-half  of  the  field  of  the  machine,  weighing  about  two  tons,  is  swung 
off  by  means  of  differential  blocks  and  an  overhead  trolley;  the  burnt 
coil  is  cut  out  with  a  hack-saw;  the  new  coil  is  slipped  over  the  tooth 
and  squeezed  into  place  by  means  of  specially-made  geared  clamps;  the 
connections  are  soldered,  taped,  and  painted;  and  the  top-field  is  then 
replaced  in  position. 

The  entire  cost  of  this  plant  does  not  exceed  $38,000,  while  its  opera- 
tion during  the  month  of  October  alone  effected  a  saving  of  $2,100, 
equivalent  to  $1  46  per  ton  of  ore  crushed,  and  reducing  the  total  mill- 
ing cost  to  $2  32  per  ton;  a  fairly  low  figure  for  a  high-priced  camp 
(wages  $4  per  day)  such  as  Bodie. 

At  present  the  plant  is  operating  most  smoothly,  and  is  successfully 
demonstrating  the  effectiveness  and  simplicity  of  the  single-phase  syn- 


—  25  — 

chronous  system  for  such  work  and  distances,  while  the  daily  saving 
over  the  use  of  steam,  on  twelve-hour  runs,  is  from  $35  to  $40. 

The  writer  takes  pleasure  in  acknowledi^ing  the  aid  of  his  assistant, 
Mr.  R.  C.  Turner,  E.M.,  in  the  preparation  of  the  accompanying 
drawings. 

EXTENSION    OF    THE    SYSTEM. 

The  availability  of  electric  power;  the  readiness  with  which,  after  it 
is  once  introduced,  it  can  be  applied  to  any  extensions  of  surface  plant 
or  new  works  such  as  continually  arise  in  progressive  mining,  has  been 
recently  demonstrated  in  our  experience  at  Bodie. 

For  the  rapid  handling  of  the  tailings,  which  were  to  be  treated  in 
large  vats  by  a  leaching  process,  it  became  necessary  to  put  up  an 
incline  track  about  1,400  ft.  away  from  the  mill.  To  haul  the  cars 
up  this  grade  by  electric  power  all  that  was  required  was  to  put  in  a 
15  horse-power  direct-current  generator  at  the  mill,  belt  it  to  the  motor, 
and  take  current  at  500  volts  to  a  10  horse-j^ower  motor  at  the  top  of 
the  incline.  This  is  being  done,  the  balance  of  5  horse-power  to  be  used 
in  lighting  the  leaching-plant  and  operating  the  necessary  pumps. 

With  electricity  this  transmission  of  power  to  the  new  plant  was 
extremely  simple.  By  rope  or  other  means  it  would  have  been  expen- 
sive, costly  to  maintain,  and  much  less  efficient. 


The  following  description  of  the  transmission  plants  of  the  San  Miguel 
Consolidated  Gold  Mining  Company,  of  Telluride,  Colo.,  and  of  the 
Willamette  Falls  Electric  Company  of  Portland,  Oregon,  is  taken  from 
"  Long-Distance  Transmission  for  Lighting  and  Power,"  by  Charles  F. 
Scott,  being  a  paper  read  at  the  general  meeting  of  the  American 
Institute  of  Electrical  Engineers,  Chicago,  111.,  June  7,  1892: 

"  The  test  of  practical  operation  in  long-distance  transmission  has 
been  applied  in  but  few  cases,  and  the  severe  test  of  continued  operation 
over  a  considerable  length  oif  time  is  of  rare  occurrence.  The  latter  is 
the  crucial  test,  and  its  commercial  significance  gives  it  the  highest 
importance.  The  continued  and  successful  operation  of  one  plant  for  a 
year,  under  extreme  conditions  of  situation  and  service,  is  of  higher 
value  in  testimony  to  the  practical  development  and  possibilities  of 
electrical  work  than  many  elaborate  projects,  or  the  operation  of  novel 
apparatus  for  a  short  time. 

"  It  is  with  this  idea  in  mind  that  a  description  is  here  to  be  given  of 
two  plants,  one  for  lighting  and  the  other  for  transmission  of  power. 
The  conditions  which  have  been  met  include  a  very  considerable  dis- 
tance, extreme  difficulties  of  climate  and  roughness  of  country,  exacting 
requirements  in  continuity  of  service,  and  a  pressure  above  that  ordina- 
rily used  in  the  class  of  machines  employed.  The  plants  to  be  described 
are  the  first  of  their  type  installed  in  this  country,  and  the  apparatus 
in  the  power-plant  is  of  a  kind  that  has  not  been  heretofore  used.  The 
type  and  construction  of  the  machines,  and  the  arrangement  of  appa- 
ratus, are  new  in  many  particulars,  and  as  they  have  contributed  largely 
to  successful  operation  they  will  be  described  with  some  minuteness. 
Alternating-current  machinery  is  employed,  constructed  by  the  West- 


—  26  — 


Lighting-Plant  at  Portland.    Diagram  of  Apparatus  and  Connections. 

inghouse  Electric  and  Manufacturing  Company,  the  pioneer  company 
in  alternating  work  in  this  country. 

"  The  lighting-plant  was  first  installed.  It  is  operated  by  the  Wil- 
lamette Falls  Electric  Company,  of  Portland,  Oregon.  The  general 
requirements  are  those  which  electrical  transmission  is  admirably 
adapted  to  meet.  The  falls  of  the  Willamette  River,  at  Oregon  City,  in 
the  combined  points  of  size,  accessibility,  and  nearness  to  the  seaport, 
are  unequaled.  These  falls,  estimated  at  from  200,000  to  250,000 
horse-power,  are  about  13  miles  from  Portland,  and  it  requires  but  a 
moment's  thought  to  appreciate  the  value  of  an  agent  which  can  make 
this  power  available  in  the  city. 

"The  Willamette  River  is  about  one  quarter  of  a  mile  wide,  and  the 
fall  is  about  40  ft.  The  present  station  is  located  on  an  island  at  the 
middle  of  the  river.  Victor  wheels  of  300  horse-power  are  geared  to 
horizontal  shafts,  from  which  the  dynamo  belts  pass  to  an  upper  floor 
at  an  angle  of  45*^.  Two  alternating-current  dynamos  for  incandescent 
lighting  are  driven  by  each  wheel.  The  current,  at  a  pressure  of  4,000 
volts,  passes  directly  to  the  line  of  No.  4  B.  &  S.  wire,  which  is  carried 
on  ordinary  double-petticoat  glaSs  Insulators  across  the  level  country  to 
a  sub-station  in  Portland.  The  current  is  received  at  3,300  volts  by 
transformers  in  the  sub-station  and  is  reduced  to  1,100  volts,  for  dis- 
tribution by  various  circuits  through  the  city  to  ordinary  transformers, 
by  which  it  is  reduced  to  50  or  100  volts. 

"  When  the  apparatus  was  designed  it  was  not  considered  practicable 
to  generate  4,000  volts  with  the  ordinary  type  of  machine,  in  which  the 
wire  is  wound  upon  the  surface  of  the  armature  on  account  of  the  diffi- 
culty of  insulating  for  more  than  1,000  or  2,000  volts.  The  work  was 
undertaken  with  a  new  type  of  armature,  which  is  specially  noteworthy, 
as  it  has  rendered  high  potentials  practicable  in  a  machine  of  simple 
construction. 


—  27  — 


Section  of  Armature,  showing  Iron  Disk  with  three  Coils  in  place. 

"  The  field  of  the  dynamo  is  of  the  ordinary  type  of  alternating-cur- 
rent machine  in  use  in  this  country.  The  casting  is  circular  in  form, 
with  twelve  inwardly  projecting  poles  of  laminated  iron,  on  which  the 
field-coils  are  placed.  This  type  of  machine  combines  simplicity  with 
rigidity  and  strength,  as  both  bearings  and  the  lower  field  are  in  one 
casting. 

"  The  armature  is  built  up  of  laminated  disks,  which  are  punched 
with  twelve  T-shaped  teeth.  The  armature-coils  are  wound  in  a  lathe, 
are  carefully  taped  and  insulated,  and  are  then  placed  over  the  teeth 
and  sprung  in  under  the  projections.  The  space  between  adjacent  coils 
is  filled  by  a  block  of  wood,  which  holds  them  in  place  securely.  This 
form  of  construction  gives  all  the  advantages  of  machine  winding  over 
hand  work,  allows  ample  insulation  between  coils  and  core,  protects  the 
coils  from  mechanical  injury,  holds  them  in  position  without  the  use  of 
band  wires,  and  makes  the  replacing  of  a  damaged  coil  comparatively 
simple.  The  field  current  is  supplied  from  a  direct-current  machine, 
and  the  main  current  is  taken  from  two  collecting-rings  on  the  arma- 
ture-shaft. The  reducing-transformers  are  placed  in  a  vault  in  the  sub- 
station at  the  city.  They  are  arranged  in  banks  or  units  of  ten.  Each 
bank  is  supplied  by  a  separate  dynamo,  and  has  a  capacity  of  1,250 
16-candle-power  lights.  The  coils  of  the  transformers  are  separately 
wound  and  taped,  and  are  separated  from  one  another  and  from  the 
irons  by  strips  of  wood.  The  primaries  are  connected  in  series  for 
receiving  3,300  volts,  and  the  secondaries  are  in  series  for  delivering 
1,100  volts,  so  that  there  are  330  volts  in  the  primary  and  110  volts  in 
the  secondary  of  each  converter.  This  method  of  connection  throws 
small  differences  of  potential  in  any  single  coil,  and  permits  the  use  of 
conductors  of  good  size.  The  necessity  for  special  insulation  is  between 
the  coils,  where  there  is  ample  room  for  placing  it.  A  transformer  may 
be  readily  cut  out  of  circuit  by  short-circuiting  its  terminals,  and  in 
case  of  an  accident  in  which  a  coil  becomes  short-circuited,  the  E.  M.  F. 


—  28  — 

on  that  transformer  disappears,  and  the  others  are  called  upon  to  do  a 
larger  share  of  the  total  work  without  interfering  with  service.  The 
efficiency  of  the  transformer  at  full  load  is  96  per  cent. 

"The  plant  was  first  installed  with  two  incandescent  machines,  and 
started  nearly  two  years  ago.  Since  that  time  five  additional  machines 
have  been  added,  so  that  there  are  now  seven,  each  with  a  capacity  for 
supplying  1,250  16-candle-power  lights,  in  Portland.  The  total  capacity 
is  8,750  lights.  The  dynamos  run  admirably.  There  was  one  night 
when  several  armature-coils  were  burned  out,  which  was  attributed  to  an 
iron  wire  falling  across  the  main  line  and  connecting  several  of  the  cir- 
cuits, grounding  them.  Otherwise  there  have  been  no  difficulties  to 
speak  of  with  regard  to  the  operation  of  the  machines.  The  Superin- 
tendent of  the  plant  states  that  the  line  has  given  very  little  trouble, 
much  less  than  would  ordinarily  be  expected  from  a  city  line.  He  also 
says  that  '  the  converters  in  the  sub-station  have  not  given  one  minute 
of  trouble,  and  have  not  cost  one  cent  for  repairs.^  One  explanation  of 
the  success  of  the  plant  is  the  intelligent  policy  of  the  General  Manager, 
in  harmony  with  his  statement  that  'It  is  not  the  first  cost  which 
counts,  but  the  cost  of  throwing  out  and  replacing  apparatus.' 

"  The  same  policy  has  happily  governed  the  installation  of  the  second 
plant  to  be  described — the  power-plant.  This  is  located  near  Telluride, 
Colo.,  and  is  owned  by  Mr.  L.  L.  Nunn.  The  Gold  King  mill  requires 
power  for  operating  its  crushers  and  stamps,  and  fuel  can  come  only 
from  long  distances  at  enormous  costs.  A  few  miles  from  the  mill  there 
is  a  water-power,  but  the  country  between  the  two  points  is  steep  and 
rough,  and  for  many  months  in  the  year  is  covered  with  snow.  Elec- 
tricity is  the  one  means  of  getting  the  power  from  its  source  to  the  mill. 
The  conditions  are  of  the  most  favorable  character  for  demonstrating 
the  value  and  possibility  of  electrical  transmission. 

"  In  this  plant  a  Pelton  wheel,  receiving  water  through  a  2  ft.  steel 
pipe,  under  a  head  of  320  ft.,  drives  an  alternating-current  generator. 
The  current  is  carried  over  a  line  of  bare  wire  to  the  mill,  which  is 
nearly  3  miles  distant,  and  drives  an  alternating-current  synchronous 
motor  of  100  horse-power.  The  generator  and  motor  are  machines  of 
the  same  size  and  form  of  construction  as  the  dynamos  at  Portland, 
already  described,  and  differ  from  these  only  in  some  minor  modifica- 
tions. 

"The  generator  is  provided  with  a  composite  field  winding.  A  part 
of  the  magnets  are  excited  by  direct  current  from  a  separate  machine, 
and  the  rest  are  excited  by  a  current  from  the  generator  armature, 
which  is  proportional  to  the  main  current,  and  is  commutated  by  the 
equivalent  of  a  two-part  commutator.  The  adjustment  is  such  that  the 
E.  M.  F.  on  the  main  terminals  rises  as  the  current  delivered  by  the 
machine  increases,  compensating  for  line-losses  and  keeping  the  pressure 
at  the  motor  3,000  volts.  The  speed  is  833  revolutions,  giving  10,000 
alternations  per  minute.  The  switch-board  and  regulating  appliances 
are  similar  to  those  in  the  station  at  Portland.  Ordinarily  no  adjust- 
ment is  required  after  the  machine  is  started,  and  the  attendant 
has  little  to  do  besides  looking  after  the  mechanical  running  of  the 
apparatus. 

"  When  the  motor  is  running,  the  only  things  to  be  cared  for  are  the 
brushes  and  the  bearings.  The  high-tension  brushes — the  only  point 
besides  the  switches  where  the  high  tension  is  exposed — will  run  for  a 


Synchronous  Motor-Plant  at  Telluride.    Diagram  showing  Apparatus  and  Connections. 


week  without  adjustment,  the  exciter  brushes  run  without  sparking,  and 
the  lubrication  of  the  bearings  is  well  provided  for.  The  construction 
and  operation  of  the  motor  are  strikingly  simple  in  comparison  with 
the  steam  engine,  which  it  replaces,  with  its  many  moving  parts  and 
intricate  motions. 

''A  few  points  illustrating  the  characteristics  of  the  synchronous 
motor  may  be  mentioned,  as  they  are  of  both  theoretical  and  practical 
interest.  The  connection  of  the  motor  to  the  generator  is  not  a  delicate 
operation.  If  the  motor  is  running  above  synchronous  speed  at  the  time 
of  connection  with  the  generator,  it  instantly  adapts  itself  to  the  proper 
speed.  If  the  motor  speed  is  slightly  lower  than  that  of  the  generator, 
it  may  fall  into  step  when  the  switch  is  closed,  but  if  it  be  running  con- 
siderably slower  it  will  not  come  into  synchronism,  but  will  further 
decrease  in  speed.  When  this  occurs,  the  switch  of  the  large  motor  is 
opened  and  that  of  the  starting-motor  is  closed,  bringing  the  machine 
up  to  full  speed  again  without  any  injury  to  the  apparatus.  If  the  E. 
^I.  F.  upon  each  of  the  machines  before  connecting  them  be  3,000  volts 
it  will  remain  unchanged  when  they  are  connected.  If  the  field-current 
of  either  machine  be  increased,  the  E.  M.  F.  will  be  raised,  but  the  field- 
current  of  the  other  machine  may  be  lowered  and  the  resulting  E.  M.  F. 
made  equal  to  3,000  volts.  The  current  flowing  between  the  machines 
depends  upon  the  relative  field-charges,  and  is  least,  whatever  the  load 
may  be,  when   the   two  machines  are  equally  or  very  near   equally 


—  30  — 

excited.  The  field-current  of  either  machine  may  be  made  zero,  and 
the  motor  will  still  run,  but  with  greatly  reduced  capacity.  In  a  test 
with  machines  of  a  smaller  size  the  E.  M.  F.  was  2,000  volts  when  the 
two  field-charges  were  equal.  When  the  field-charge  of  either  machine 
was  cut  out  it  fell  to  1,200  volts  and  the  current  increased  very  con- 
siderably. 

"  The  efficiency  of  the  synchronous  motor  system,  leaving  out  loss  in 
conductors,  but  including  losses  in  generator  and  motor  in  the  plant  for 
the  delivery  of  50  horse-power,  was  found  to  be  83^  per  cent  at  full  load, 
and  74  per  cent  at  half  load. 

''  Full  load  may  be  thrown  on  the  motor  suddenly.  In  the  Gold  King 
mill  the  stamps,  which  are  operated  by  the  motor,  are  usually  left  raised 
when  the  plant  is  stopped,  in  order  to  avoid  the  extra  strain  of  lifting 
them  when  the  plant  is  started.  It  sometimes  happens  that  the  stamps 
are  left  down  and  the  motor  is  required  to  raise  them  all  at  once.  When 
the  clutch  is  thrown  in,  the  current  indicates  that  the  load  is  consider- 
ably above  the  normal  capacity  of  the  motor,  and  yet  it  is  started  with- 
out difficulty  or  apparent  strain. 

"  The  excellent  current  regulation  with  different  loads,  the  tendency 
of  the  machines  to  normal  adjustment  when  there  is  ordinary  variation 
in  the  field-currents,  the  small  liability  to  injury  when  the  motor  is 
greatly  overloaded,  the  high  efficiency  and  ease  of  attendance,  are  points 
of  great  value  in  the  practical  operation  of  the  system. 

"  The  pole-line  runs  from  the  power  station  up  the  mountain  to  a 
height  of  2,500  ft.,  and  then  crosses  a  rough  but  comparatively  level 
country  to  the  mill.  The  line  at  some  places  is  at  an  angle  of  45°,  and 
many  of  the  poles  had  to  be  set  in  solid  rock.  The  surface  of  the  snow 
in  winter  is  occasionally  at  a  level  with  the  tops  of  the  poles,  and  parts 
of  the  pole-line  are  practically  inaccessible  during  some  months  of  the 
year.  This  region  is  peculiarly  subjected  to  lightning  discharges,  and 
special  precautions  are  necessary  to  protect  the  apparatus.  In  one 
instance  there  were  forty-two  discharges  of  the  lightning-arresters  in  as 
many  minutes. 

"  The  plant  was  started  for  regular  work  in  June  of  last  year.  An 
accurate  record  was  kept  from  the  middle  of  July  to  the  first  of  May, 
showing  the  actual  number  and  the  length  of  the  delays  caused  by 
electrical  machinery.  During  these  nine  and  a  half  months  the  system 
was  in  regular  continuous  operation  six  and  a  half  days  each  week,  with 
but  few  intermissions.  The  difficulties  which  were  encountered  were 
insignificant  in  amount  and  have  resulted,  not  from  any  fundamental 
difficulty  in  the  system,  but  have  been  caused  by  incidental  defects  or 
accidents  which  usually  indicated  their  own  remedy.  The  stops  due  to 
the  electrical  machinery  resulted  from  a  variety  of  causes,  and  comprised 
the  replacing  of  an  armature-coil  damaged  by  lightning,  renewing  of 
fuses,  fixing  loose  contacts,  the  examination  of  the  line  after  a  storm, 
and  sundry  other  slight  mishaps.  The  aggregate  time  lost  on  account 
of  the  electrical  apparatus  was,  by  actual  count,  less  than  48  hours 
during  three  fourths  of  a  year.  A  recent  report  from  the  Superintendent 
of  the  plant,  covering  the  time  from  December  13th  to  May  1st,  shows 
that  the  plant  was  running  127  days  with  a  loss  of  19|  hours,  or,  as  he 
puts  it,  an  average  of  about  nine  minutes  in  a  day  of  24  hours.  Although 
the  plant  was  generally  shut  down  each  week  for  12  hours  on  Sunday, 
this  was  not  practicable  during  a  part  of  the  winter,  and  the  motor  on 


Plate  VIII.    Machine  used  as  Generator  and  Motor  at  Telluride,  Colorado. 


Plate  IX.    New  Motor  at  Telluride,  Colorado.     250  horse-power. 


%HI7BRSIT7 


©»• 


^iXPO 


one  occasion  was  run  continuously  for  27  days  without  any  stop  whalteyer. 
Such  a  record  as  this,  with  a  new  type  of  machinery,  in  a  country^, 
where  line  construction  and  maintenance  are  peculiarly  difficult,  with--^'^' 
practically  continuous  service,  with  attendants  who  were  not  electricians, 
with  a  high  voltage,  a  considerable  distance  and  large  power,  places 
transmission  by  the  alternating-current  synchronous  system  beyond  the 
stage  of  experimental  trial  and  gives  it  the  stamp  of  commercial  success. 

"  This  success  is  confirmed  in  a  substantial  way  by  the  immediate 
extension  of  the  plant.  A  50  horse-power  motor  is  now  being  installed 
at  a  mill  a  few  miles  from  the  Gold  King;  an  order  has  been  entered  for 
a  750  horse-power  generator  to  be  located  in  the  power  station;  and  a 
250  horse-power  motor  for  operating  a  mill  about  10  miles  distant. 
Lighting  at  Telluride,  8  miles  from  the  station,  which  has  been  done 
heretofore  on  a  small  scale  on  a  circuit  from  the  power  generator,  is  being 
extended.* 

"The  large  generator  is  a  new  design  and  is  notable,  as  it  has  more 
than  three  times  the  capacity  of  any  alternating-current  dynamo  pre- 
viously made  in  this  country.  Two  machines  of  this  size  have  been 
running  for  some  months  for  incandescent  lighting  at  St.  Louis. 

"This  dynamo  is  of  a  type  similar  to  the  machines  at  Portland  and 
Telluride.  The  field  has  twenty-eight  poles,  requiring  a  speed  of  570 
revolutions  for  16,000  alternations,  the  conditions  of  running  at  St.  Louis, 
and  357  revolutions  for  10,000,  as  it  will  be  operated  at  Telluride.  The 
armature  has  T-shaped  teeth,  as  in  smaller  machines.  The  diameter  ■ 
of  the  armature  is  slightly  over  4  ft.  and  its  length  is  about  2  ft. 
There  is  a  third  bearing  at  the  end  of  the  shaft  outside  of  the  pulley  to 
relieve  the  other  bearings  from  the  severe  strains  resulting  from  belt 
tension.  The  total  height  of  the  machine  is  8  ft.,  and  its  weight  is  40,000 
lbs.     The  electrical  efficiency  at  full  load  is  over  95  per  cent. 

"The  extension  of  alternating-current  working,  both  for  lighting  and 
power,  by  the  use  of  large  machines,  is  therefore  already  provided  for. 

"  The  extension  to  greater  distances  is  largely  a  question  of  E.  M.  F. 
Nearly  every  one  is  familiar  with  the  rapidity  with  which  the  cost  of 
copper  diminishes  as  the  voltage  is  increased.  If  the  cost  be  $100  with 
600  volts,  it  will  be  $25  at  1,000  volts,  and  $1  at  5,000  volts.  The  higher 
the  tension,  however,  the  greater  the  difficulty  and  ccst  of  construction, 
and  the  greater  the  liability  to  accident  with  apparatus  and  line.  There 
are  a  few  points  in  connection  with  this  subject  which  may  be  noted 
without  entering  into  a  general  consideration  of  it. 

"The  smallest  size  of  wire  that  can  well  be  used  for  line  work  on 
account  of  its  mechanical  strength  is  about  No.  6  B  &  S.  This  wire  will 
transmit  with  20  per  cent  loss  100  horse-power  10  miles  at  4,000  volts,  or 
twice  the  power  half  the  distance.  Unless  these  distances  or  powers  are 
to  be  exceeded,  an  increase  in  pressure  would  result  in  no  saving  in  cop- 
per, but  simply  in  a  less  line-loss,  which  is  already  not  excessive. 

*  Note,  May,  1893. — Since  this  paper  was  read  the  750  horse-power  generator,  the  50 
horse-power  motor,  and  the  250  norse-power  motor  have  been  installed  and  put  in 
operation.  (See  Plates  VIII  and  IX.)  The  order  has  been  placed  for  an  additional  75 
horse-power  motor.  A  letter  from  the  engineer  of  the  plant,  dated  April  20,  1893,  con- 
tains the  following:  "  The  generator  runs  very  nicely  indeed.  The  motors  are  running 
very  satisfactorily.  The  250  norse-power  is  running  verv  nicely  at  the  present  time.  The 
50  horse-power  has  been  running  about  a  week  since  the  winter  shut-down,. and  the  100 
horse-power  motor,  which  has  been  idle  during  repairs  to  the  mill,  is  expected  to  start 
within  two  weeks.  When  we  get  the  75  horse-power  motor  and  start  it,  we  will  feel  that 
we  have  quite  a  system  in  operation." 


—  32  — 

'^The  use  of  4,000  volts  at  the  motor  and  a  line-loss  of  20  per  cent 
requires  an  outlay  for  copper  of  only  about  10  to  15  per  cent  of  the  total 
cost  of  the  plant  when  the  distance  is  10  miles.  Unless,  therefore,  the 
cost  of  copper  is  to  bear  an  insignificant  proportion  of  the  total  cost,  it 
is  unnecessary  to  exceed  this  pressure  unless  the  distance  be  greater 
than  about  10  miles. 

"These  simple  considerations  show  that  pressures  practically  the 
same  as  those  employed  in  the  plants  which  have  been  described  are 
ample  for  considerable  distances.  The  same  type  of  apparatus  which 
has  been  successful  in  them  is  available  for  larger  capacities.  The  fun- 
damental elements  required  for  electrical  transmission  in  a  very  wide 
range  of  cases  have  therefore  been  tried  and  their  success  demonstrated. 

"  For  considerably  longer  distances.,  where  pressures  higher  than  about 
5,000  volts  are  required,  good  practice  indicates  the  use  of  transformers 
for  raising  the  pressure  at  the  generator  and  reducing  it  at  the  motor, 
similar  in  general  to  those  employed  at  Portland.  The  increased  pres- 
sure thus  available  greatly  reduces  the  cost  of  copper  required,  and  this 
reduction  must,  of  course,  be  more  than  sufficient  to  cover  the  cost  of 
the  transformers. 

"  The  simplicity  and  flexibility  and  range  of  the  alternating-current 
system  make  its  possibilities  the  sole  dependence  of  the  largest  enter- 
prises toward  which  the  public  and  engineers  are  looking.  The  records 
of  the  plants  at  both  Portland  and  Telluride  demonstrate  that  these 
possibilities  are  being  realized,  and  that  work  in  this  field  is  fast  passing 
from  experimental  investigation  into  practical  electrical  engineering." 

PROTECTION   AGAINST   LIGHTNING. 

The  protection  of  these  circuits  against  lightning  is  a  very  important 
matter.  The  mountainous  regions  in  which  the  majority  of  mines  are 
located  are  generally  subject  to  severe  thunder-storms  and  electrical 
disturbances,  and  therefore  to  the  miner  using  electrical  power,  it  is  of 
vital  importance  to  have  his  apparatus  protected  from  damage  from 
such  causes;  while  many  may  be  deterred  from  undertaking  the  installa- 
tion of  electric  transmissions  through  fear  of  lightning  interfering  too 
seriously  with  their  successful  operation. 

During  the  past  year  much  trouble  has  arisen  at  Bodie  from  this 
cause;  the  machines  running  smoothly  and  perfectly  for  several  weeks, 
when  a  storm  would  occur,  oftentimes  without  visible  lightning  or 
audible  thunder,  but  causing  a  burn-out  of  armature-coils  in  generator 
or  motor. 

Lightning-arrester  houses  have  been  built  at  each  end  of  the  line  close 
to  the  power-house  and  motor-room,  and  these  fitted  up  with  banks  of 
spark-gap-arresters  and  choke-coils  precisely  as  outlined  by  Mr.  Alex.  J. 
Wurts  in  his  article  on  "  Discriminating  Lightning-Arresters  and  Recent 
Progress  in  Means  for  Protection  against  Lightning  "  (in  the  "Electrical 
Engineering  Magazine,"  May  23,  1894),  since  which  time  but  little 
trouble  has  been  had. 

Our  experience  was  so  similar  to  that  of  Mr.  Wurts  with  the  plant  of 
the  San  Miguel  Consolidated  Gold  Mining  Company,  at  Telluride,  Colo., 
and  so  much  interesting  and  valuable  information  on  the  subject  is 
given  in  the  above-mentioned  article,  that  the  writer  takes  the  liberty 
of  quoting  Mr.  Wurts  in  full: 


—  33  T- 

An  Experiment  with  Lightning-Arresters  on  a   3,000-Volt  Alternating- 
Current  Circuit.* 

"  During  the  winter  of  1892  and  1893  I  made  a  searching  investigation 
of  this  subject,  experimenting  with  disruptive  discharges  and  various 
kinds  of  combinations  of  apparatus  which  might  promise  advantageous 
results,  and  since  that  time  have  spent  nearly  six  months  in  the  State 
of  Colorado — a  land  of  thunder-storms — testing  the  various  forms  of 
apparatus  which  I  had  designed  as  a  possible  protection  against 
lightning. 


TO    THE  LINE. 


^M 


GROUND 
TO   THE    CINERATQR 


TO   THE    GENERATOR 


TO  THE  GENERATOR 


F15.I5. 


"The  general  requirements  of  efficient  lightning-arrester  apparatus 
are:  (1)  To  provide  discharge  circuits  which  shall  operate  automatically 
and  repeatedly,  and  which  shall  with  certainty  avoid  dynamo  short- 
circuits  or  interruption  of  the  system.  (2)  To  provide  discharge  cir- 
cuits, or  so  install  them  that  they  shall  invariably  ofler  a  certain  path 
to  ground  for  disruptive  discharges  in  preference  to  any  other  part  of 
the  system.  It  follows  also  from  this  last,  and  as  a  matter  of  practical 
experience,  that  ground-discharge  circuits  should  be  short  and  straight, 

*  Abstract  of  a  paper  read  at  the  eleventh  general  meeting  of  the  American  Institute 
of  Electrical  Engineers,  Philadelphia,  May  15,  1894. 


—  34  — 


and  that  ground  connections  should  be  of  the  most  approved  construc- 
tion. Experiments  were  therefore  made  to  determine  the  number  of 
non-arcing  metal  cylinders  and  spark-gaps  which  would  be  necessary 
to  interrupt  a  short-circuit  on  a  3,000-volt  alternator  with  the  potential 
raised  to  3,300  volts.  Nineteen  cylinders,  or  eighteen  gaps,  were  found 
to  offer  ample  margin,  and  the  breaking  down  E.  M.  F.  on  half  this 
number  of  gaps,  which  would  intervene  between  line  and  ground,  was 
found  to  be  about  70  per  cent  of  the  E.  M.  F.  required  to  break  down 
insulation  ordinarily  used  in  a  3,000-volt  generator.  The  form  finally 
adopted  was  that  of  a  fiat  coil  about  18  in.  in  diameter,  and  wound  with 
seventeen  turns  of  wire;  the  size  of  the  wire  varied,  of  course,  with  the 
carrying  capacity  of  the  particular  circuit  into  which  it  was  to  be 
connected.  After  further  experimenting  with  various  combinations  of 
spark-gaps  and  choke-coils,  it  was  decided  that  the  trial  apparatus  could 
consist  of  eight  choke-coils  and  twelve  1,000-volt  non-arcing  metal- 
arresters  for  each  end  of  each  circuit;  that  is,  four  choke-coils  should  be 
connected  in  series  in  each  leg  of  each  circuit,  with  discharge  circuits 
intervening.  The  relative  positions  of  these  parts  are  clearly  indicated 
in  Fig.  16,  which  represents  one  end  of  each  of  the  three  circuits.  Dis- 
ruptive discharges  form  nodal  points  in  the  system ;  that  is,  points  where 
there  will  be  a  minimum  tendency  to  discharge;  hence  to  avoid  these 
with  any  degree  of  certainty  a  multiplicity  of  arresters,  preferably  line- 


•    •    •    i- 


Fig. 17. 


arresters,  should  be  used.  Choke-coils  form  points  of  reflection,  or  points 
where  there  will  be  a  maximum  tendency  to  discharge;  hence,  a  dis- 
charge spark-gap  connected  directly  in  front  of  a  choke-coil  is  more 
likely  to  receive  discharges  than  if  placed  at  some  other  point  in  the 
system.  Disruptive  discharges  are  liable  to  divide  and  follow  several 
paths,  being  governed  by  a  complexity  of  ever-varying  circumstances. 
For  this  reason  it  was  decided  to  connect  several  choke-coils  in  series, 
so  that  should  only  a  portion  of  a  discharge  pass  across  the  first  arrester, 
the  balance  passing  through  the  first  coil,  a  second  opportunity  for 
discharge  would  be  found  at  the  second  arrester,  which  was  also  con- 
nected in  front  of  a  coil,  and  therefore  at  a  point  of  reflection.  Should 
this  remaining  portion  of  the  discharge  again  divide,  a  further  oppor- 
tunity for  discharge  would  be  aftbrded  at  the  third  arrester,  and  so  on, 
so  that  by  the  time  the  fourth  coil  was  reached  it  was  presumed  that 
the  discharge  would  have  spent  itself. 

"Some  of  the  many  experiments  made  to  substantiate  this  theory  are 
exceedingly  interesting  as  well  as  instructive.  Referring  to  Fig.  17,  a 
are  the  terminals  of  a  powerful  influence-machine,  b  is  a  battery  of  Ley- 


—  35  — 

den  jars,  g  a  wire  which  may  represent  the  ground,  and  is  connected  to 
the  outside  coating  of  the  jars;  l  is  a  second  wire  which  may  represent 
one  leg  of  an  electric  circuit;  a,  b,  c,  and  d  are  choke-coils  connected 
with  the  line  l,  and  in  series  with  each  other;  2,  3,  4,  and  5  are  inter- 
vening discharge-circuits  containing  spark-gaps;  1  is  a  -l^f  in.  spark- 
gap  separating  line  l  from  the  inside  coating  of  battery  b.  If  now  the 
battery  becomes  charged  from  the  influence-machine  a,  a  large^  and  vio- 
lent disruptive  discharge  will  take  place  across  gap  1,  and  suddenly 
charge  line  l.  This  discharge  will  then  pass  to  earth  g  through  one  or 
more  of  the  spark-gaps  2,  3,  4,  5,  according  to  circumstances.  It  will 
be  noted  now,  that  this  arrangement  of  choke-coils  and  discharge- circuits 
is  similar  to  that  shown  in  Fig.  16.  The  spark-gaps  were  made  of 
rounded  ^  in.  brass  rod  adjustable  with  a  -^^^  in.  screw  thread.  The 
coils  were  wound  with  No.  0000  wire,  were  3  in.  in  diameter,  6  in.  long, 
and  contained  eleven  turns  each. 

"  With  these  four  choke-coils  in  series,  and  spark-gaps  intervening, 
the  discharges  are  so  thoroughly  sifted  out  that  only  an  occasional 
thread-like  spark  finds  its  way  across  the  last  gap.  With  laboratory 
results  such  as  these,  it  seems  fair  to  presume  that  results  more  or  less 
similar  might  also  be  expected  in  practice. 

"  The  plant  selected  for  the  trial  of  this  apparatus  was  that  of  the  San 
Miguel  Consolidated  Gold  Mining  Company,  of  Telluride,  Colorado, 
which  is  equipped  with  a  3,000-volt  alternating-current  synchronous 
system,  of  1,000  horse-power  capacity,  operating  stamping  mills,  and 
furnishing  current  to  the  Telluride  Electric  Light  Company.  These 
points  are  situated  among  the  mountains  at  distances  varying  from  3 
to  10  miles  from  the  power-house.  Three  separate  circuits  leaving  the 
power-house  extend  over  a  wild  and  rocky  country,  and  in  some  places 
rise  above  timber  line.  In  previous  years  every  attempt  to  protect  this 
plant  from  lightning  had  failed.  During  the  summer  months  two  Horses 
were  kept  constantly  saddled  ready  for  emergencies  consequent  on  light- 
ning discharges,  and  at  the  motor  and  power-house  it  was  common  prac- 
tice, on  the  approach  of  a  thunder-storm,  to  lay  out,  ready  for  instant 
use,  an  extra  armature-coil,  with  all  the  necessary  tools  for  handling 
the  same.  In  one  of  the  former  types  of  arresters  used  in  this  plant 
forty  fuses  were  blown  inside  of  sixty  minutes. 

"The  apparatus  was  then  installed  in  a  specially  constructed  and 
weather-proof  lightning-arrester  house,  the  arresters  and  choke-coils 
being  mounted  on  thoroughly  dried  wooden  frames,  and  every  precau- 
tion taken  to  insulate  these  from  the  ground  and  from  each  other.  In 
this  manner,  also,  it  was  expected  that  the  lightning  discharges  would 
be  kept  entirely  out  of  the  station.  The  connections  inside  the  power- 
house lightning-arrester  house  are  all  clearly  indicated  in  Fig.  16.  One 
main  B.  &  S.  No.  3  ground-wire  was  used  for  all  the  arresters  in  each 
bank,  unnecessary  kinks  and  bends  being  studiously  avoided. 

"Observations  were  taken  by  competent  men  at  each  bank  of  arresters 
during  the  entire  lightning  season,  and  the  results  obtained  indicate  that 
the  discharges  occurred  most  frequently  over  the  second  arresters;  many 
passed  over  the  third  arresters;  very  few,  however,  over  the  first  or  fourth. 
The  writer  personally  watched  one  of  these  banks  of  arresters  through 
severe  thunder-storms,  and  in  every  instance  the  discharges  noticed  by 
him  were  seen  to  pass  across  the  second  series  of  spark-gaps,  but  in  no 
instance  was  there  a  fuse  blown  or  damage  done  to  the  arresters." 


—  36  — 

The  matter  of  proper  earth  connections  at  the  terminals  of  the  ground- 
wires  from  these  lightning-arresters  is  most  important.  The  common 
idea  that  a  rod  of  iron  stuck  into  the  earth  a  couple  of  feet,  or  a  piece 
of  old  iron  thrown  into  the  bed  of  a  stream,  forms  a  good  "ground"  is 
most  erroneous,  as  has  been  proven  by  our  experience  at  Bodie.  In 
reality,  such  form  the  poorest  kind  of  earth  connection. 

The  ground-wires  from  the  banks  of  arresters  are  carried  into  a  pit 
dug  directly  underneath  the  arrester-house.  This  pit  is  about  4  ft. 
square  and  reaches  to  permanently  moist  earth  at  the  power  station, 
while  at  the  mill,  since  no  damp  ground  was  found  at  a  reasonable 
depth,  it  was  necessary  to  carry  a  i  in.  pipe  into  the  pit  through  which 
water  is  occasionally  allowed  to  run.  On  the  bottom  of  the  pit  a  layer 
of  small  charcoal  2  ft.  in  depth  was  laid,  and  on  this  placed  a  plate  of 
copper  -^^  in.  in  thickness  and  6  sq.  ft.  in  area.  To  this  plate  the  ground- 
wire  was  securely  soldered  in  a  spiral  coil,  and  another  layer  of  charcoal 
placed  on  top  of  it,  after  which  the  pit  was  filled  up  with  loose  dirt. 
This  makes  an  efficient  ground,  and  gives  the  necessary  surface  for  the 
rapid  dissemination  of  the  electric  discharge. 

Inductive  resistance-grounds  have  also  been  added  at  either  end  of 
the  line,  with  the  object  of  preventing  damage  to  the  machines  through 
static  charges,  by  leaking  them  to  earth  as  fast  as  accumulated.  They 
are  connected  to  each  side  of  the  line  as  shown  in  sketch,  and  their 
resistance  is  sufficiently  high  to  prevent  any  appreciable  loss  of  current. 


aavvvvnI 


^/VNAAA/V 

_S2_ft_ 


Fij-IB. 


Main   Line. 


Two  50- volt  lamps  in  the  secondary  circuit  of  each  "  resistance  "  burn 
at  a  dull  red  when  the  switch  S  is  closed;  as  is  the  case  at  all  times 
excepting  during  thunder-storms.  During  such  these  grounds  are  taken 
off  in  order  to  prevent  danger  of  burning  out  the  primaries. 

These  inductive  resistances  are  chiefly  of  service  during  wind-storms, 
when  the  line  is  most  liable  to  cumulative  charges  from  the  atmosphere. 


ELECTRICAL   TRANSMISSION    PLANTS   AT    PRESENT    IN   OPERATION. 

The  following  short  descriptions  of  electrical  power  plants  in  oper- 
ation have  been  culled  from  various  sources,  many  of  them  from  the 
article  by  W.  H.  Adams  in  "  Ens;ineering  and  Mining  Journal,"  June  23, 
1894 : 

Electric  Generating  Station  at  Tivoli. — In  a  lecture  delivered  by  Prof. 
J.  A.  Fleming,  at  the  Royal  Institution,  the  following  description  was 
given  of  a  plant  used  in  transmitting  2,000  horse-power  from  the  Falls 
of  the  Anio,  Tivoli,  for  18  miles  over  the  Campagna  to  Rome:  "  From  the 
upper  levels  of  the  Anio  an  aqueduct  has  been  led  which  delivers  water 
to  the  top  of  an  iron  pipe  150  ft.  above  the  power-house.  This  power- 
house is  placed  about  halfway  down  the  declivity  on  which  are  situated 
the  famous  cascades  of  Tivoli.  The  pipe  is  about  2  meters  in  diameter 
and  can  deliver  100  to  150  cu.  ft.  of  water  a  second  with  a  head  of  150 
ft.,  or  nearly  2,000  horse-power.  The  water  is  conducted  to  a  series  of 
nine  Girard  turbines,  six  being  of  350  and  three  of  50  horse-power.  The 
six  larger  ones  are  directly  connected  with  Ganz  alternators,  which  gen- 
erate a  current  of  electricity  at  a  pressure  of  6,000  volts,  while  the  three 
smaller  ones  are  used  to  drive  the  exciters.  The  current  is  conveyed  to 
Rome  by  four  cables  carried  on  760  posts,  which  are  placed  in  a  straight 
line  across  the  Campagna.  Outside  the  Porta  Pia,  at  Rome,  it  enters 
a  transformer-house,  where  its  pressure  is  reduced  from  5,000  to  2,000 
volts.  Part  is  then  used  for  arc  lighting  in  the  streets  of  Rome,  and  the 
rest  is  distributed  by  underground  cables  to  various  other  centers,  where 
it  is  again  transformed  down  to  a  pressure  of  100  volts  for  use  in  houses. 
About  20,000  incandescent  lamps  are  thus  supplied  with  current." 

Compagnie  de  VIndustrie  Electrique^  Geneve,  Switzerland. — Four  hun- 
dred horse-power  transmitted  20  miles  by  continuous  currents,  potential 
between  6,000  and  7,000  volts.  One  400  horse-power  turbine,  under 
fall  of  14  meters,  revolves  on  vertical  shaft  at  120  revolutions  per  minute, 
and  drives  by  means  of  bevel  wheels  and  pinions  two  dynamos,  placed 
one  on  each  side.  Commercial  efficiency  of  the  dynamos  reaches  93  per 
cent,  with  a  weight  less  than  1\  tons.  Commercial  efficiency  of  the 
installation  from  shaft  of  the  turbine  to  the  motor  shafts  exceed  75  per 
cent  at  full  load.  Bare  copper  conductors  are  used  in  line  construction, 
7  millimeters  in  diameter,  the  line  being  entirely  aerial  through  mount- 
ainous country  between  Frinvilliers  and  Bieberist. 

A  plant  at  Oynuax,  France,  has  been  working  satisfactorily  for  some 
time  with  two  turbines  of  150  horse-power  each.  A  generator  of  105,000 
watts  capacity  at  2,000  volts  is  directly  connected  to  each  turbine. 
Distance  between  generating  and  receiving  station  about  8  kilometers, 
and  76  per  cent  efficiency  is  obtained  in  the  transmission. 

At  Chamhery,  2,000  horse-power  is  about  being  installed  with  water- 
fall 2,040  ft.  high.  There  are  to  be  seven  alternators,  each  of  120  kilo- 
watts at  5,000  volts. 

The  two  waterfalls  about  25  miles  from  Christiania,  Norway j  eire  about 
to  be  utilized  for  power  transmission,  at  a  total  cost  of  $1,500,000.  The 
voltage  will  not  exceed  20,000,  to  be  carried  on  bare*  wire  on  poles  care- 
fully guarded  over  the  entire  distance. 

The  Portland  General  Electric  power  plant,  at  Oregon  City,  Oregon,  12 
miles  from  the  city  of  Portland,  on  the  Willamette  River,  will  install 
12,000  horse-power,  using  twenty  Victor  42  in.  and  twenty  Victor  60  in. 


—  38  — 

turbines,  under  30  and  48  ft.  head.  Many  new  features  in  tri-phase 
transmission  are  promised  for  this  plant,  one  half  of  which  is  now  being 
installed  for  service  during  the  coming  year. 

In  the  Baltic  mill,  on  the  Shetucket  River,  about  5  miles  above  Taft- 
ville,  Connecticut,  the  General  Electric  Company  has  lately  installed  a 
three-phase  power  transmission  plant  of  1,500  horse-power,  using  three 
double  42  in.  horizontal  turbines,  developing  800  effective  horse-power 
each  at  157  revolutions  per  minute,  and  one  double  27  in.  turbine  devel- 
oping 300  horse-power  at  244  revolutions  per  minute. 

The  efficiency  is  just  80  per  cent  from  power  applied  to  dynamo  pulley 
to  delivery  at  motor  pulley  at  Columbia,  South  Carolina.  The  Columbia 
Cotton  Mills  Company  is  about  starting  a  plant  of  1,400  horse- power, 
using  two  pairs  of  48  in.  Victor  turbines  on  a  horizontal  shaft,  and  a 
single  24  in.  turbine  for  fire  pump.  The  48  in.  turbines  are  connected 
together,  and  at  each  end  are  directly  connected  to  a  generator  of  700 
horse-power  capacity.  This  is  the  second  instance  in  this  country  where 
an  entire  cotton  mill  is  driven  by  electricity.  The  generators,  made  by 
the  General  Electric  Company,  weigh  about  100,000  lbs.  each;  the  arma- 
ture is  10  ft.  in  diameter,  500  kilo-watts  capacity,  and  operates  at  a  speed 
of  108  revolutions  per  minute. 

Concord  Land  and  Water  Power  Company,  Concord,  N.  H.,  has  utilized 
2,000  horse-power  of  the  5,000  horse-power,  furnished  by  the  new  dam 
located  at  Sewall's  Falls.  Horizontal  turbines  are  used  with  draught 
tubes,  thus  avoiding  gears,  the  power  being  transmitted  from  each  pair 
of  wheels  to  the  shafting  in  the  generator-room  by  belts.  The  shafting 
is  arranged  with  quills  and  clutches,  in  order  that  any  wheel  or  section 
of  shaft  may  be  run  independently  of  any  other.  The  pulleys  used  on 
shafting  are  extra  heavy,  and  fly-wheels  are  being  tried  for  the  first 
time  at  this  location  for  inertia  regulation.  Six  tri-phased  generators 
are  to  be  installed,  two  being  now  in  operation,  of  250  kilo-watts  capacity 
and  separately  excited,  and  run  at  a  speed  of  600  revolutions  per  minute. 
The  current  is  generated  at  2,500  volts;  the  line  runs  to  the  center  of 
the  city,  about  3  miles,  where  tri-phased  current  of  a  frequency  of  50 
is  delivered  to  the  mains  at  2,200  volts  pressure.  It  is  then  transformed 
to  110  volts  for  delivery  to  consumers,  being  sold  by  meter  at  20  cents 
per  kw.-hour  for  lighting  and  10  cents  per  kw.-hour  for  power,  heating, 
and  cooking. 

Colorado. 

The  Roaring  Fork  Electric  Light  and  Power  Company,  Aspen. — Pipe- 
line, 500  ft.  of  16  in.,  3,500  ft.  of  14  in.  Power  plant:  eight  24  in.  Pelton 
wheels,  1,000  revolutions,  under  a  head  of  820  ft.,  equal  to  175  horse- 
power each;  total,  1,400  horse-power.  The  light  plant  supplies  the 
entire  town  of  Aspen,  as  well  as  many  mills,  mines,  and  sampling- 
works.  The  power  plant  supplies  120,000  watts,  and  is  used  for  operating 
mills,  hoists,  pumps,  and  tramways  within  a  radius  of  3  to  4  miles  from 
the  generating  station.  The  plant  has  been  in  continuous  operation  for 
five  years,  with  practically  no  expense  in  the  way  of  repairs  or  inter- 
ruption of  the  service. 

Aspen  Mining  and  Smelting  Company^s  Plants. — Flume,  1,300  ft.  long, 
head  80  ft.;  two  50  horse-power  Thomson-Houston  dynamos,  equal 
to  100  electric  horse-power;  generating  station,  6,000  ft.  from  tunnel 
entrance.  The  underground  motors  are  located  1,000,  1,200,  and  1,800 
ft.  from  the  entrance.     Power  used  for  hoisting. 


—  39  — 

New  works  of  the  Roaring  Fork  Company.  Two  pipe-lines:  2,500  ft. 
of  26  in.  pipe,  head  312  ft.;  4,300  ft.  of  24  in.  pipe,  head  330  ft.  Power 
plant:  five  60  in.  Pel  ton  wheels,  30  revolutions,  250  horse-power  each; 
total,  1,250  horse-power.     Distributes  power  5  miles  distant. 

People^s  Electric  Light  and  Power  Company,  on  Castle  Creek,  1  mile 
from  Aspen.  Power  plant:  two  5  ft.  double-nozzle  Pelton  wheels,  300 
horse-power  each,  240  revolutions,  180  ft.  head;  also  two  3  ft.  double- 
nozzle  Pelton  wheels,  75  horse-power  each,  345  revolutions.  Power  and 
light  furnished  to  mills  and  mines  within  a  radius  of  3  miles. 

Virginius  Mine  Plant. — Pipe-line,  4,000  ft.,  head  485  ft.  Power  plant: 
two  Pelton  wheels,  one  5  ft.  and  the  other  6  ft.  in  diameter,  500  and  700 
horse-power,  respectively;  total,  1,200  horse-power.  Electric  generating 
plant:  293  horse-power;  line,  4  miles  long.  Machinery  operated  at  the 
mines:  2  pumps  (one  60  horse-power  and  the  other  25  horse-power), 
one  15iiorse-power  blower,  two  60  horse-power  motors  for  running  con- 
centrators and  stamp  mills.  Previous  to  installation  of  the  electric 
plant  the  outlay  for  coal  alone  was  $40,000,  at  $18  per  ton. 

Telluride — San  Miguel  Consolidated  Gold  Mining  Company^s  Plant. — 
Power  plant:  6  ft.  Pelton  wheel,  3,900  ft.  of  24  in.  pipe-line,  320  ft.  of 
head;  1,100  horse-power  dynamos,  supplying  power  to  three  stamp 
mills,  2,  3,  and  10  miles  distant,  and  also  lights  for  the  town  of  Tellu- 
ride, 8  miles  distant.  The  pole-line  is  8,800  to  12,000  ft.  above  sea- 
level.  The  cost  of  maintenance,  including  wages  at  power  plant,  was 
given  at  $3,060  for  the  first  year.  The  repair  account  was  $21,  occa- 
sioned by  lightning.  Since  the  introduction  of  lightning-arresters  there 
has  been  no  damage. from  this  cause. 

Sheridan  &  Belmont  Company. — Water-head,  235  ft.;  Pelton  wheel, 
28  in.;  electric  circuit,  12,300  ft.,  furnishing  250  to  300  lights,  and  two 
motors  of  10  horse-power  and  5  horse-power. 

Belmont  Consolidated  Mining  Company. — Head  of  water,  670  ft.,  capa- 
ble of  developing  210  horse-power,  with  a  36  in.  Pelton  wheel.  In  the 
mine  are  two  30  horse-power  motors.  Length  of  line,  2  miles.  Loss 
between  generators  and  motors,  8  per  cent. 

Washington. 

Walla  Walla  Electric  Power  Plant. — Pipe-line,  5,800  ft.  of  48  in.  pipe; 
two  80  in.  Pelton  wheels;  two  A-lOO  Edison  2,000- volt  machines. 

Idaho. 

Cceur  d'Alene  Silver  and  Lead  Mining  Company. — Pipe-line,  3,000  ft.; 
head,  850  ft.;  two  3  ft.  double-nozzle  Pelton  wheels.  Has  replaced  all 
steam  machinery  at  the  mine,  with  a  saving  of  $40,000  per  year. 

Mr.  Clark,  General  Manager  of  this  company,  writes  in  reference  to 
this  plant  as  follows:  "In  respect  to  the  relative  merits  of  steam  and 
electricity  at  the  Poorman  Mine,  I  will  say  that  the  amount  saved  in 
fuel  is  about  $100  a  day.  This,  of  course,  is  due  to  the  fact  that  we 
generate  electricity  by  water  power.  How  electricity  would  compare 
with  steam  in  the  matter  of  cost,  if  the  former  was  generated  by  steam 
power,  I  am  not  prepared  to  say,  but  am  of  the  opinion  that  where 
steam  has  to  be  transmitted  a  long  distance  underground,  particularly 
where  it  is  wet,  that  electricity  generated  with  steam  and  transmitted 
to  the  pumps  or  other  machinery  will  be  found  to  be  the  most  econom- 


—  40  — 

ical,  the  percentage  of  loss  in  transmission  being  so  much  less;  in  addi- 
tion to  this,  the  cumbersome  steam  pipes,  with  their  destructive  effect 
on  shaft  timber,  is  avoided.  We  have  five  machines  in  use:  two  175 
K.-W.  at  the  generating  station  1 1  miles  distant  from  our  works,  where 
they  are  operated  with  Pelton  wheels  under  800  ft.  head;  one  175 
K.-W.  to  drive  our  concentrator;  one  150  K.-W.  T.-H.  machine  for  the 
pump,  raising  500  gallons  of  water  per  minute  500  ft.;  and  one  175 
K.-W.  for  the  compressor.  This  system  has  been  almost  two  years  in 
operation,  and  my  experience  in  that  time  is  that  an  electric  machine 
to  run  continuously,  as  in  operating  a  mine  pump  or  mill,  must  have  at 
least  double  the  capacity  it  would  require  when  stops  occur — as  on  a 
street  car,  for  example." 

The  greatest  departure,  however,  electrically,  is  the  installation  at 
this  mine  of  an  80  kilo-watt,  l,WO-volt  motor  for  driving  a  Knowles 
double-acting  pump,  having  a  capacity  of  lifting  500  gallons  500  ft. 
high  per  minute.  The  current  for  the  motor  is  conducted  down  the 
shaft  through  which  all  the  steam  pipes,  air  pipes,  etc.,  are  taken,  by 
two  Siemens  (lead,  iron  band,  iron  wire,  armored)  cables — C.  L.  A.  T.  W. 
The  iron  wire  armoring  of  these  two  cables  is  so  connected  and  arranged 
as  to  prevent  any  shocks  due  to  static  charges,  should  workmen  come 
in  contact  with  the  cables. 

The  regulation  of  the  speed  of  the  motor  is  effected  by  placing  in 
armature-circuit  of  motor  a  rheostat  of  two  or  three  ohms  capacity. 
The  motor  drives  the  pump  through  a  counter-shaft  and  wooden-toothed 
gear  and  bronzed  pinion.  The  crank-shaft  of  pump  makes  from  36  to 
46  revolutions  per  minute  as  desired. 

This  is  the  first  installation  of  a  1,200- volt  motor  placed  in  a  mine  for 
pumping  purposes.  The  mine  and  mill  are  lighted  by  incandescent 
lamps  from  a  110- volt  Edison  dynamo  belted  from  main  shaft  of  mill. 

California. 

The  Dalmatia  Mine  Plant  in  El  Dorado  County. — The  power  station 
is  located  on  Rock  Creek,  some  1,500  feet  below  the  mine  and  mill,  and 
2  miles  distant  in  a  straight  line.  The  plant  consists  of  an  8  ft.  Pelton 
wheel,  which,  running  under  a  head  of  110  ft.  at  100  revolutions,  with 
a  5^  in.  nozzle,  has  a  maximum  capacity  of  130  horse-power.  To  this 
wheel  is  connected  a  100  horse-power  constant-current  Brush  generator — 
30  amperes — speeded  at  900  revolutions,  the  current  from  which  is  car- 
ried to  the  mill  through  a  single  insulated  copper  wire,  No.  3,  B.  &  S. 
gauge,  the  return  being  made  by  a  wire  of  the  same  size,  making  a  4- 
mile  circuit.  The  power  from  the  generator  is  communicated  to  the 
counter-shaft  of  the  mill  by  a  70  horse-power  motor  running  at  950  revo- 
lutions. The  machinery  operated  consists  of  three  Huntington  mills,  a 
10-stamp  battery,  and  a  rockbreaker.  The  Pelton  wheel  under  these 
conditions  shows  an  efficiency  of  86  per  cent,  while  about  75  per  cent  of 
the  power  thus  generated  is  available  for  duty  at  the  mill.  Sufficient 
power  is  taken  from  the  main  circuit  to  run  sixty  incandescent  lamps 
for  lighting  the  works,  office,  and  residence  of  the  manager.  The  mill 
handles  an  average  of  4,000  tons  of  ore  a  month,  effecting  a  saving  of 
some  60  per  cent  over  the  former  method  of  working  by  steam  power, 
while  the  cost  of  maintenance  is  about  as  six  to  one  in  favor  of  electricity. 
An  extension  of  this  line  has  recently  been  made  to  the  St.  Lawrence 


—  41  — 

Mill,  similar  in  character  to  the  Dalmatia — located  3  miles  from  the 
latter  and  5.  miles  from  the  waterwheel  station — which  is  operated  by- 
Keith  generators  and  motors.  This  is  an  exceptionally  long  distance 
for  a  continuous-current  transmission. 

The  San  Antonio  Electric  Light  and  Power  Company  in  Southern  Cali- 
fornia.— The  power  plant  is  located  in  San  Antonio  Canon.  The  water 
is  brought  to  the  power  station  through  1,900  ft.  of  30  in.  and  600  ft.  of 
24  in.  double-riveted  sheet-iron  pipe,  giving  300  ft.  effective  head  or 
running  pressure.  The  power  station  is  provided  with  four  double-nozzle 
Pelton  wheels,  34  in.  in  diameter,  coupled  direct  to  the  armature  shafts 
of  as  many  Westinghouse  alternating-current  generators  of  200  horse- 
power each.  The  wheels  run  under  above  conditions  600  revolutions 
per  minute,  giving  the  same  speed  to  the  generators.  Two  exciters  are 
provided,  which  are  also  run  by  Pelton  wheels  coupled  to  the  shafts  in 
the  same  manner,  and  of  20  horse-power  each.  The  current  thus  gen- 
erated is  carried  on  two  No.  7  bare  copper  wires  7  miles  down  the  caiion 
to  a  point  where  they  diverge,  one  running  to  Pomona,  15  miles,  and 
the  other  to  San  Bernardino,  28  miles,  covering  by  the  return  circuit  in 
the  latter  case  a  distance  of  56  miles.  By  means  of  transformers  the 
potential  is  raised  at  the  generating  station  to  10,000  volts,  and  the 
current  carried  at  this  pressure  to  sub-stations  located  just  outside  the 
cities  named,  where,  by  means  of  step-down  transformers,  it  is  reduced 
to  about  1,000  volts  and  then  distributed  for  both  light  and  power  pur- 
poses. 

Amador  County — The  Cover  Plant. — A  3  ft.  Pelton  wheel,  340  ft. 
head,  speed  470  revolutions,  works  two  Dow  pumps  of  15  horse-power 
and  20  horse-power,  which  handle  200,000  gallons  of  water  per  day. 

Plant  at  Redlands,  San  Bernardino  County. — This  is  a  three-phase 
plant,  recently  installed  by  the  General  Electric  Company;  distance  of 
transmission,  5  miles;  two  A.  C.  generators,  of  250  K.-W.  each,  driven 
by  four  30  in.  Pelton  water  wheels,  at  a  speed  of  600  revolutions.  The 
generators  carry  a  potential  of  2,450  volts  and  the  motor  about  2,150, 
the  line-loss  being  approximately  12  per  cent.  The  three  No.  0,  bare 
copper  wires  (insulated  within  city  limits)  are  carried  on  deep-groove, 
double-petticoat  glass  insulators.  The  line  poles  are  35  ft.  long,  6  ft.  in 
the  ground,  and  set  110  ft.  apart.  The  one  motor  at  present  in  opera- 
tion is  a  synchronous  high-potential  machine  of  150  horse-power,  and 
has  continuous  work  to  perform  in  driving  the  ice  machines  of  the 
Union  Ice  Company.  The  initial  current  in  the  fields  of  the  motor  is 
generated  by  a  small  exciter,  and  the  motor  is  self-starting  only  under 
light  load,  the  full  load  being  thrown  on  after  the  machine  is  up  to 
speed. 

Nevada. 

The  Chollar  Plant. — This,  one  of  the  earliest  applications  of  electricity 
to  mining  work,  has  already  been  so  fully  described  in  the  mining  and 
technical  papers  that  it  is  not  necessary  to  repeat  the  details. 

Arizona. 

Plant  of  the  Commercial  Mining  Company. — This  plant  consists  of  a 
4  ft.  Pelton  wheel,  which  runs,  under  a  1,200  ft.  head,  at  699  revolutions  a 
minute,  developing  45  horse-power,  using  a  nozzle  tip  j^-^-^  in.  in  diameter; 
also  a  24  in.  Pelton  wheel  running,  under  the  same  head,  at  1,380  revo- 


—  42  — 

lutions,  developing  20  horse-power,  with  a  nozzle  tip  ■^-u%  in.  diameter. 
These  wheels  run  a  concentrating  and  smelting  plant,  including  rock- 
breaker,  blowers,  pump,  etc.  The  pipe-line  is  20,000  ft.  in  length,  the 
upper  end  being  6  and  5  in.  casing,  and  the  lower  end  5  in.  lap-weld  pipe. 

ELECTRICITY    IN   UNDERGROUND   OPERATIONS. 

This  power  was  applied  earlier  and  has  been  more  widely  used  in  the 
coal  measures  than  in  lode  or  precious  metal  mining;  hence,  in  the  former 
we  find  many  coal  mines  fitted  with  extensive  and  efficient  electric 
haulage  systems  and  lit  by  electricity,  while  their  drills  and  coal-cutters 
are  operated  by  the  same  power. 

Electric  locomotives  are  now  built  no  larger  than  the  cars  they  are  to 
haul,  and  made  to  conform  to  any  gauge  of  track  from  18  in.  upwards, 
effacting  a  great  saving  in  the  size  of  entries  required  for  narrow  coal 
seems.  That  they  do  not  vitiate  the  air  as  do  steam  motors  is  a  great 
point  in  their  favor. 

For  the  operation  of  undercutting  machines,  haulage,  and  general  coal 
mining  work,  the  direct-current  is  usually  employed,  since  it  can  be 
generated  cheaply  at  the  pit's  mouth,  and  the  underground  workings  are 
not  usually  of  such  length  as  to  increase  unduly  the  cost  of  conductors. 

It  is  not  invariably  employed,  however,  as  instanced  in  the  First 
Pool  Mines  at  Benola,  on  the  Monongahela  River,  where  an  A.  C.  three- 
phase  plant  was  installed  several  years  ago.  The  generator  is  of  100 
horse-power,  Tesla  type,  operating  under  500  volts.  The  three  wires 
are  carried  underground  for  2^  miles  along  the  main  entr3\  Clark's 
insulated  wire,  No.  2,  is  used,  and  branches  are  carried  to  the  various 
chambers  to  operate  McMichael's  undercutting  machines  working  in  the 
bituminous  coal-seam  from  6  to  8  ft.  wide.  The  current  is  used  for 
lighting  also,  in  16  candle-power  incandescent  lamps. 

New  electric  coal-cutters  are  continually  being  put  upon  the  market,* 
and  the  improvement  in  these  machines  and  the  introduction  of  electric 
pick-machines  for  hard  coal,  typifies  the  rapid  advance  in  the  applica- 
tion of  electricity  to  mining  work. 

In  metal  mining,  electricity  has  thus  far  been  employed  chiefly  for 
pumping  and  hoisting,  though  its  field  will  undoubtedly  be  greatly 
extended  within  the  next  decade. 

While  it  is  reported  that  electric  percussion  drills  are  at  present  in 
successful  use,  and  exposed  to  the  same  hard  usage  as  the  air  drills,  f 
the  writer  has  not  yet  been  fortunate  enough  to  witness  such  nor  to 
obtain  details  of  their  operation  underground. 

The  use  of  electricity,  however,  certainly  admits  of  a  great  saving  in 
the  transmission  from  air-compressor  to  drills,  by  the  placing  of  the 
former  underground  and  closer  to  the  stopes  and  headings. 

That  motors  are  now  made  that  will  operate  as  successfully  under- 
ground and  in  damp  places,  as  upon  the  surface,  is  conclusively  shown  by 
the  number  of  pumps  at  work  in  wet  shafts  to-day.  By  this  it  is  not 
meant  to  say  that  wet  electric  motors  will  operate,  but  that  these  are 
now  so  insulated  and  protected  that  they  successfully  exclude  the  moist- 
ure of  wet  shafts  and  damp  foundations. 

A  most  excellent  instance  of  this  we  have  at  hand  in  Superintendent 

*  See  "Engineering  and  Mining  Journal,"  June  16,  1894,  p.  559. 
+  Trans.  Am.  Inst.  M.  Engineers,  vol.  xxiii,  p.  405. 


^^^ 


%iriVBI^SITY 


Call's  letter  to  the  writer,  descriptive  of  the  Gover  Mining  Coi^patTy's    ^'* 
(Amador  County,  Cal.)  plant,  as  follows:  '  ^^.^ 

"  Two  triple-plunger  Dow  pumps  are  used — one  with  6  in.  plungerSj^^jL 
raising  12^  miner's  inches  of  water  341  ft.  vertically,  and  one  with  5  in."* 
plungers,  raising  11  miner's  inches  of  water  208  ft.  vertically. 

"  An  Edison  dynamo.  No.  16,  of  50  horse-power  capacity,  is  used,  and 
run  at  a  speed  of  820  revolutions  per  minute,  the  voltage  being  220. 

"  Sprague  motors  are  used.  The  one  working  the  larger  pump  is  run 
at  a  speed  of  1,000  revolutions  per  minute,  giving  20  horse-power;  and 
the  other  is  run  at  a  speed  of  1,250  revolutions  per  minute,  producing 
15  horse-power.  The  voltage  in  the  motors  is  the  same  as  that  of  the 
dynamo. 

'•  Copper  wire  y\  in.  in  diameter  transmits  the  power  from  the  dynamo 
to  the  motors,  a  distance  of  about  1,700  ft. — 1,000  ft.  on  the  surface,  and 
700  feet  down  the  shaft.  (See  Plate  X.)  The  wires  cause  no  trouble 
whatever  in  the  shaft,  retimbering  even- being  done  without  stopping  the 
pumps.     The  shaft  is  quite  wet  in  places. 

''  The  pumps  have  run  three  years  and  four  months,  pumping  during 
that  time  59,000,000  gallons  of  water. 

'VThe  armature  of  the  dynamo  burnt  out  once,  owing  to  injuries 
received  in  shipment,  the  core  being  shifted.  The  commutator  of  the 
dynamo  is  turned  down  about  once  a  year. 

''The  motors  are  connected  with  the  pumps  by  gearing.  Rawhide 
pinions  are  used  on  the  armature  shafts.  The  rawhide  pinions  last  a 
year,  and  are  more  reliable  and  more  satisfactory  than  those  made  of 
bronze. 

"  With  the  motors,  the  only  precaution  taken  against  dampness  is  a 
thorough  coat  of  paraffine  paint.  The  smaller  motor  was  run  at  one 
time  for  several  hours  with  the  field  piece  half  way  under  water." 

In  hoisting,  electricity  Ijas  thus  far  been  applied  chiefly  to  inclines 
and  used  in  motors  of  comparatively  small  capacity  or  from  10  to  40 
horse-power,  but  its  field  will  undoubtedly  be  extended  to  vertical  shafts 
and  larger  machines  as  its  advantages  become  more  widely  recognized. 

In  the  mines  of  the  Aspen  Mining  and  Smelting  Company,  at  Aspen, 
Colorado,  three  hoists  are  in  operation  underground,  each  of  the  two 
main  hoists  raising  250  tons  up  a  60°  incline  250  ft.  long  every  twenty- 
four  hours.  A  25  horse-power  motor  in  use  there  raises  3,000  lbs.  up  a 
similar  slope  275  ft.  per  minute,  and  is  capable  of  making  the  round 
trip  from  a  depth  of  550  ft.  in  three  minutes. 

This  plant  was  installed  three  years  ago,  and  direct-current  machines 
are  used  throughout.  The  rapid  development  of  the  A.  C.  systems  during 
the  past  few  years  has  demonstrated  the  advantages  of  the  two-phase 
current  for  both  transmission  of  the  power  and  the  accomplishment  of 
a  variety  of  work  at  the  delivery  end  of  the  line. 

This  is  shown  in  the  following  description  from  the  "  Colliery  Guardian  " 
of  the  recent  installation  of  such  a  plant  at  the  Decize  collieries  in  France. 
A  noticeable  feature,  and  one  already  alluded  to  as  a  decided  advantage 
of  the  system,  is  the  ready  regulation  of  varying  load  on  the  two  currents: 

*'One  of  the  most  interesting  cases  of  the  electrical  transmission  of 
power  for  coal-mining  purposes  in  Europe  has  been  completed  and  set  in 
operation  at  the  Decize  collieries,  in  the  Nievre  Department  of  France, 
and  which  are  owned  by  MM.  Schneider  &  Co.  This  installation  is 
remarkable  from  the  fact  that  diphase  alternating-currents  are  employed 


—  44 


for  the  transmission,  and  diphase  alternating-current  motors  are  used 
for  reconverting  the  electrical  energy  into  mechanical  power  at  the  dif- 
ferent pits.  In  designing  this  plant  the  problem  to  be  solved  was  to 
erect  a  central  generating  station  for  the  distribution  of  electrical  energy 
at  the  different  pits  where  it  could  be  utilized  in  electro-motors  for 
operating  ventilating  fans,  hauling  machinery,  pumps,  and  for  lighting 
purposes.  A  general  idea  of  what  had  to  be  accomplished  is  shown  in 
the  annexed  table: 


Site. 

Distance 
from 
Generating 
Station- 
Yards. 

Electrical  Machinery  or  Lamps  Receiv- 
ing the  Current  Transmitted. 

1.— West. 
Puits  des  Chagnats 

5,090 
3,466 
2,058 
1,084 

30  horse-power  electric  motor.* 

.... 30  horse-power  electric  motor.* 

30  horse-power  electric  motor.* 

Electric 

Fendue  des  Lacets 

Puits  des  Coupes '. 

Puits  des  Zagots 

2.— Generating  Station. 
Various  installations 

hauling  machine  of  15  horse-power. t 
-Six  arc  and  100  incandescent  lamps.J 

..     .     __ 30  horse-power 

3.— East. 
Fendue  des  Marizy       _-. 

1,300 
2,490 
3,250 

Sorting  and  washing  shops  of  the 
Pr6-Charpin 

electric    motor    and   24    arc    lamps.§ 
-  ..                  500  incan- 

Champvert  

descent  lamps  of    16  candle-power.J 
,  12  horse-power  electric  motor.  || 

*  Used  for  ventilating  fan.    t  Inclined  plane.    X  Lighting, 
ing.     i  Pumping. 


Ventilating  fan  and  light- 


"The  generating  station  is  situated,  respectively,  at  distances  of  from 
3.1  miles  and  1.86  miles  from  the  extreme  points  which  have  to  be  sup- 
plied with  current.  It  contains  a  battery  of  six  boilers  and  two  units 
(steam  engines  and  dynamos),  each  of  a  capacity  of  100  kilo- watts;  a 
further  unit  will  shortly  be  laid  down.  The  two  units  may  be  worked 
singly  or  in  parallel.  The  engines  are  of  the  horizontal  non-condensing 
type,  running  at  200  revolutions  per  minute,  and  driving  the  diphase 
alternators  by  means  of  belting.  A  notable  feature  in  this  connection 
is  the  fact  that  each  electrical  unit  comprises  a  twin  alternator,  or  in 
reality  two  machines,  placed  one  at  each  end  of  the  shaft,  the  driving 
pulley  carrying  the  engine  belt  being  arranged  in  the  middle  of  the 
shaft.  Of  course,  in  a  case  like  the  present,  where  current  is  employed 
both  for  lighting  and  for  power  purposes,  one  of  the  circuits  may  become 
more  loaded  than  another,  and  in  this  event  the  equilibrium  must  be 
established  by  varying  the  ratio  of  the  electro-motive  forces.  The  arrange- 
ment adopted  in  the  Decize  installation  allows  of  this  being  accomplished, 
as  each  of  the  two  circuits  having  a  distinct  field,  it  is  only  necessary  to 
vary  the  exciting  current  by  means  of  rheostats  to  get  the  desired  effect. 
The  generators  introduced  are  Zipernowsky  ten-pole  alternators,  with 
revolving  field  magnets.  The  ten-field  magnets  are  connected  together 
in  series,  and  the  exciting  current  is  led  to  them  by  means  of  two  metallic 
rings  carried  on  an  extension  of  the  driving  shaft  on  the  opposite  side 
to  that  of  the  driving  pulley — that  is  to  say,  on  an  outer  extension  of 
the  shaft.  Two  ordinary  brass  brushes  press  upon  these  rings,  to  which 
the  exciting  current  is  furnished  by  a  direct-current  dynamo.  This 
latter  machine  is  operated  by  a  belt  from  the  shaft  of  the  alternator. 
At  900  revolutions  a  minute  this  direct-current  dynamo  supplies  the 


—  45  — 

exciting  current  for  the  twin  alternator,  being  between  25  and  30  amperes 
at  110  volts.  The  fixed  armature  of  the  alternators  is  formed  of  ten 
coils,  any  one  of  which  can  be  withdrawn  and  replaced  with  little  trouble. 

''After  passing  through  the  switch-board,  the  current  is  transmitted 
mainly  by  means  of  overhead  wires  to  the  points  of  utilization,  the  only 
portion  laid  underground  being  toward  the  end  of  the  principal  line  lead- 
ing to  the  Chagnats  pit.  The  wires  forming  the  overhead  line  are  of 
silicon-bronze,  and  are  carried  on  porcelain  insulators  attached  to  poles 
24  ft.  high.  The  diameter  of  the  wires  constituting  the  principal  line  to 
the  western  part  of  the  district  is  6  mm.,  and  4  mm.  in  the  case  of  the 
remainder  of  the  line.  It  is  noteworthy  that  the  same  poles  carrying 
the  transmission  wires  also  support  telephone  wires,  the  latter  being 
arranged  12  ft.  from  the  ground.  In  order  to  counteract  the  effects  of  induc- 
tion in  the  telephone  wires,  the  line  conductors  are  crossed  at  distances 
averaging  540  yds.,  and  by  this  means  the  difficulty  of  understanding 
conversation  along  the  telephone  wires  which  use  the  earth  as  return, 
has  been  overcome.  The  small  portion  of  underground  line  forms  a 
lead-covered  cable,  laid  in  a  wooden  conduit,  as  also  does  the  telephone 
line  for  the  same  distance.  Suitable  lightning  conductors  are  provided 
at  the  generating  and  distributing  sub-stations  and  at  intervals  along 
the  line..  The  electro-motors  at  the  sub- stations,  where  the  current  is 
utilized  for  the  different  purposes  mentioned  in  the  table  given  above, 
are  of  the  same  type  as  the  generators.  These  diphase  motors  are  easily 
set  in  operation,  and  are  to  all  intents  and  purposes  left  to  themselves 
for  several  hours  together.  The  only  attention  they  receive  is  the  visit 
of  an  employe  every  six  or  eight  hours  to  ascertain  whether  the  motors 
are  working  properly.  The  sub-stations  are  situated  in  the  forest,  and 
the  facility  of  working  on  this  system  as  compared  with  the  erection  in 
each  place  of  a  boiler,  steam  engine,  and  ventilating  fan,  is  considered 
to  be  remarkable,  apart  from  the  question  of  the  cost  of  transporting 
fuel." 

The  advantages  of  electric  power  both  above  and  under  ground,  in  point 
of  cleanliness,  compactness,  ease  of  transmission,  etc.,  have  been  so  often 
dwelt  upon  that  it  is  only  surprising  they  have  not  been  more  often 
availed  of  by  miners  everywhere.  The  next  decade  will  undoubtedly  see 
a  wonderful  development  in  the  application  of  electricity  to  mining 
operations. 


>*^  Of  THK 


;£iyo; 


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